I wrote a work in progress guide to the mythic 5 man dungeon achievements. Here's a link to the original Reddit post if you want to read it there.
Here's the (so far) unedited copy/paste of the Reddit post.
Hey-ho neighbor-inos. Every expansion my friends and I test ourselves by rushing the dungeon achievements as fast as we can, and since I've been doing them so early into the expansion, I figured I'd compose a list of how we personally handled each achievement and give any tips/information I can on it (since finding good information at this point is a bit hard when you rely on crap-tier WOWHead comments, most of which are erroneous and just stupid jokes, but I digress)
Anyways, this isn't some perfect lexicon of knowledge or anything, it's just how I did the achievements and my personal advice on how to do it. I'll also rate them by difficulty, so feel free to try proving me wrong on that. I'm also going to express what I think would be the best group setup for the achievements, but again, this is only my personal advice so don't think it's any end-all-be-all.
This is, of course, a work in progress as me and my friends go through the achievements. I will expand on this as we work through them. Until then, I hope the list helps you and let me know if you might have anything worth adding to my advice or if you catch any errors.
Thanks. And have a fun.
---
-BLACK ROOK HOLD-
There are two boss achievements here, as well as a really shitty RNG-based pseudo-achievement that is part of the achievement meta but can thankfully be done on Heroic and possibly Normal as well.
BLACK ROOK MOAN;
"Defeat Amalgam of Souls after killing a Frustrated Soul in Black Rook Hold on Mythic difficulty"
Boss; The Amalgam of Souls
Optimal Setup: One Tank, One Healer, Three DPS.
Difficulty: Easy.
This is a pretty simple achievement and it's very, very easy depending on what sort of CC your group has. Long-term in-combat stuns such as Blind, Root or Polymorph will make this achievement almost pointlessly simple, but it can still be done if your group only has short-term stuns or only slows/pushbacks. Anyways, you pull the boss like normal and proceed to DPS it down. Once the boss reaches 50% health, it will enter Phase 2. This is where the achievement will happen.
A number of Tortured Souls will spawn on the outskirts of the room, they look like the banshee models. They will try to move towards the boss and you will need organized handling of them to perform the achievement without wiping. One soul needs to be marked out as the CC soul. The others must be killed, as having only two or three of them reach the boss may be enough to wipe the group. The CC'd soul must be rooted, stunned, slowed, snared, pushed back or anything else you can do to prevent the soul from touching the boss. After around 40ish seconds the Tortured Soul will turn into a Frustrated Soul (I don't think there's any raid alert for this, it simply turns red and grows slightly larger, so keep an eye on it).
At this point you need to kill it as quick as you can, as it will still try to reach the boss. After the Frustrated Soul is dead, burn the boss down like normal and the achievement is complete.
After Notes: Long-term Roots or CC make this achievement very easy. So long as you make sure to get the soul you have marked for CC locked down and burn down the rest of the souls, the achievement doesn't take much. Druids and Mages make the achievement very easy, but it's already a fairly easy achievement to begin with.
ADDS? MORE LIKE BADS;
"Defeat Illysanna Ravencrest without killing any of her allies in Black Rook Hold on Mythic difficulty"
Boss; Illysanna Ravencrest
Optimal Setup; Two Tanks, One Healer, Two DPS.
Difficulty: Medium.
While the mechanics of the achievement are simple, pulling it off might be a little hard depending on your group set up. As the achievement describes, you just need to kill Gender Bent Illidan without killing any of the adds she summons. As far as I can tell, she summons the adds once her energy bar reaches 100, so it's very much worth it to pop any major DPS cooldowns you have on her right away and zerg her health as low as you can get it before the adds even join the fight. Once the adds are out, you have no choice but to either have someone tank them away from the group or carefully avoid using AoE and cleaves, as the adds don't have a very large health pool. She summons one melee add with around 11 million health and oine mage add with around 9 million health.
The melee adds is annoying and does a Shockwave-esque ability that can be avoided by moving away from the mob while he casts it. The mage add spams an Arcane Blast-esque spell that deals damage to the group and gives him a stacking buff increasing his damage by 100%. You really should keep the made add either stunned or interrupted to allow the buff some time to fall off. Either way, keep them both tanked away from the group, or carefully avoid AoEing them if you only have one tank, and all you have to do is down the boss.
Not a very hard achievement, but groups that can have a DPS swap to tank for the fight will have a much easier time, as the mobs are fairly annoying and while they don't deal a lot of damage, it's better to have one person dedicated to controlling them. With a second tank handling the adds, the melee add's shockwaves don't bother the group and you can keep the mage add interrupted to avoid too many stacks from building up.
After Notes: Not much to it. Pretty straightforward achievement, you just need the gear and organization to deal with it. I don't know if the fight can go on long enough for another set of adds to spawn, but with our poor gearscores (we can't even queue for heroics, hurkhurkhurk) we only ever saw a single set of adds, so it shouldn't be an issue.
YOU USED TO SCRAWL ME IN YOUR FEL TOME;
"Find all entries of Illysanna Ravencrest's diary in Black Rook Hold, then feel accomplished for completing your crappy pseudo-achievement. In Black Rook Hold"
This achievement is really stupid, but required for the meta. All you do is keep a lookout for Illysanna's diary pages. I do not know where they all spawn, I've found two different ones in Lord Ravencrest's Chambers right before the last boss. There are Six different pages in total and they may, or may not, spawn at random each time you enter the dungeon. From what I can tell, you can do it on Normal difficulty so you may *at least* have the option of grinding the dungeon in order to complete the achievement, I don't know.
-ASSAULT ON VIOLET HOLD-
There are another two boss achievements to obtain in this dungeon, both fairly easy. The only issue is that it's totally RNG-dependent as to whether or not you get the bosses you need. Because it's Mythic, you can only do it once per week. What amazing foresight issued by the good potato-filled-sacks-sitting-at-computer-desks down at Blizzard!
I MADE A FOOD!;
"Defeat Festerface after slaying a Black Bile in Assault in Violet Hold on Mythic difficulty"
Boss; Festerface
Optimal Setup; It don't matter. None of this matters.
Difficulty: Very Easy.
While the boss fight itself may prove to be a bit difficult, the achievement is trivialized by Violet Hold's unique mob-control mechanic. Under normal circumstances this achievement might stand to be one of the most difficult of them all, but because you can insta-kill the Black Bile add with the containment nodes, the achievement is rendered to being quite easy to perform. All you need to do is pull the boss and begin the encounter. Green goo adds called Congealed Goo will spawn, these adds will begin to AoE the group. These need to be killed ASAP. However, unlike the fight would normally go, where the tank kites Festerface to the downed goo piles in order to get rid of them, you must allow the goo piles to remain so Festerface can build energy. Eating goo piles removes 25 energy from the boss, and you need to let the boss build to 100 energy in order to spawn the Black Bile add.
You can use the containment nodes to insta-kill the Congealed Goo if you absolutely can't keep them DPS'd down (they reform a few seconds after death if not eaten by the boss, so you can see how this can quickly become an issue). Once Festerface reaches 100/100 energy, he will cast the "Uh Oh!" spell, spawning the Black Bile. The Black Bile has around 13 million health and the fight can get very tough at this stage. If you can't handle it, or simply don't want to, just hit a couple of the containment nodes and the Black Bile will instantly be destroyed. After the Black Bile is dead, finish off the boss and the achievement is completed.
After Notes: Not much to say on this one. If you're having issues surviving the Congealed Goo AoE, consider letting the boss eat a couple. Each one removes 25 of boss' energy, but it might be necessary if you simply can't out-heal the damage. If it's really a problem, consider bringing in two healers as DPS isn't much of an issue with this fight or the achievement linked to it.
YOU'RE JUST MAKING IT WORSE!;
"Defeat Millificent Manastorm after she becomes very cross with you in Assault on Violet Hold on Mythic difficulty"
Boss; Millificent Manastorm
Optimal Setup; One Tank, One Healer, Three DPS.
Difficulty: Easy.
Not only is this achievement a pain in the ass due to the fact it is RNG-reliant, but you also need to have the Manastorm's Duplicator toy from Warlords of Draenor (at this point, everyone reading this immediately suffers major heart failure and dies). This means if you did not get the toy in WoD, you're going to have to go back to your fucking Garrison, build a fucking Inn (if you didn't have one), Upgrade the fucking Garrison to fucking Level 2 (if it wasn't already past level 1) and then fucking wait for fucking Millhouse fucking Manastorm to fucking show up in your fucking Inn and get his fucking quest to go to fucking Blackrock fucking Spaghettiland and get the fucking Iron Star Dildo from the fucking room before the fucking last fucking boss. After that, simply turn in the quest and you will have the Manastorm's Duplicator.
Once you have this toy, the achievement is "simple". All you need to do is use the toy during the boss fight with Millificent Manastorm. Upon using the toy, she will immediately strike you with the spell Millificent's Ire, dealing 2 million damage (before resistances, I believe it's shadow damage? Not sure, but it's mitigated by some resistance or another). I'm not sure if only one person in the group needs to do this or if everyone does, but we had everyone do it just in case. It's not terribly difficult to survive, you just need to pop every single survivability cooldown you have and it should be okay. Tanks will have an easy time mitigating practically all the damage, and I'm assuming Rogues can probably just Cloak of Skill to avoid it, same with Ice Blocks, Paladin bubbles and spells like that. At any rate, just pop everything you have.
The one hang up to this is that if you die, you're basically shit out of luck because death will remove the toy effect and you'll be stuck waiting for its whopping two hour long cooldown. Point suggested; don't die. After you survive the 2 million burst, all you need to do is down the boss like normal.
After Notes: Not a hard achievement, just a real bitch. Like I said, maybe only one person needs to do it in order for the entire group to get the achievement, but I'm unsure as we had all five people pop it just to be better safe than sorry. This one is very punishing due to the fact that if you die to her 2 million spike, you'll either have to wait two hours to try again or you'll just have to try again some other time. Of course, the achievement DOES mention NOTHING about surviving the burst, so it may be entirely possible to get the achievement even if she killed you. Like I said, I already have the achievement so additional information is welcome in order to answer this.
-MAW OF SOULS-
Maw of souls has three achievements you'll need to get, with one of them being a massive bitch and probably one of the hardest achievements in the game (unless I am wrong about how it works, we have not done it as of yet, but more on this later, gator). At any rate, the achievements here are slightly more difficult than a lot of the other dungeons, so be prepared to be tested.
INSTANT KARMA;
"Defeat Ymiron after defiantly striking down 6 Risen Warriors in Maw of Souls on Mythic difficulty"
Boss; Ymiron, the Fallen King
Optimal Setup; Two Tanks, Two Healers, One DPS.
Difficulty: Hard.
This is a somewhat technical achievement as it requires you to defeat the boss while pulling an outside trash mob into the fight. The trash mob in question is one of the two Seacursed Soulkeepers found in the stretch between the dungeon entrance and Ymiron. One of the Seacursed Soulkeepers is part of the very first trash pull and should be killed. The second is standing directly in front of Ymiron, and this is the one you will be using for the achievement. The achievement is simple in mechanic but quite hard in execution. How this works is, the Seacursed Soulkeeper uses an ability called Defiant Strike, which appears to be some cone/360 AoE strike that deals quite a bit of magic damage. Ymiron, during the fight, casts a spell called Bane. This summons swirling purple puddles on the ground that, if not soaked by players, eventually spawn skeleton adds called Risen Warriors. You will need to pull the Seacursed Soulkeeper into the fight, allow Ymiron to spawn at least 6 Risen Warriors and then have the Seacursed Soulkeeper kill the Risen Warriors with its Defiant Strike. The good news is that a single Defiant Strike is all it takes to kill the Risen Warriors. The bad news is that this is going to be a huge bitch. First of all, the Seacursed Soulkeeper hits like a truck who is in an abusive drunken relationship.
Hitting around 400k on tanks with melee strikes alone, I am unsure if it's possible this early in the expansion for a single tank to tank both the Seacursed Soulkeeper and Ymiron. Your second tank should keep the Soulkeeper away from the boss and the group, avoiding the Defiant Strikes as best they can. Don't be afraid to DPS the Soulkeeper down a bit. With some 11 million health, they can take quite a beating (wink wink) and only need to be alive long enough to Defiant Strike the skeleton adds down. Of course, if you kill the Soulkeeper and then wipe on Ymiron you have failed the achievement and will have to either reset the instance or wait for next week. The Soulkeeper should only be killed once you're fairly certain you can also down Ymiron. The Bane phase of the fight will be a mess, especially with the Soulkeeper mucking about. You only need to have 6 Risen Warriors spawn and if you soak none of the Banes, far more than that will appear from the unsoaked Banes, which can be an issue if the Soulkeeper decides not to Defiant Strike quickly enough.
You can comfortably soak 4-5 Banes without worrying about not enough Risen Warriors spawning. Once the skeletons are up, the Ymiron tank should AoE them to obtain aggro and the Soulkeeper tank should bring their mob to the boss. Once the Soulkeeper casts its Defiant Strike and blows up the skeletons, you can pop DPS cooldowns and burn Ymiron and the Soulkeeper down. This will be a tough test of your tank's endurance as well as your healers' ability to heal, especially if you do a 2 tank, 2 heal 1 dps set up. The best comp for mythics at the moment is 2 tank, 1 heal, 1 disc priest, 1 dps and this will probably be the best set up you could ask for when it comes to this achievement.
After Notes: While it MIGHT be possible at the moment to do this achievement with one tank, I really highly doubt it. The Seacursed Soulkeepers are a project of their own to tank, hitting for rather high damage and having Defiant Strike charges to worry about. The one good thing about this achievement is that if you do mess up and kill the Soulkeeper and then wipe on Ymiron you can at least reset the instance and get the trash to respawn. This might take a few wipes to get right, but it's not an impossible achievement to get, especially if you get good at managing the Bane phases (we were awful at it).
HELHEIM HATH NO FURY;
"Rescue the Captured Val'kyr in Maw of Souls on Mythic Difficulty"
Boss; Harbaron
Optimal Setup; One Tank, One Healer, Three DPS.
Difficulty: Hard.
I admit that I am a bit unsure just how this achievement goes, but I will describe it as best I understand. Essentially, immediately after defeating Ymiron, a hidden counter starts to tick down. If you've ever done execution runs in the old Stratholme or Shattered Halls instances, then you know how this works. You have a set amount of time to reach the second boss in order to save the Captured Val'kyr mob. The counter, as I said, is hidden and makes this sort of a pain. All you can do is quickly skip the cutscene, zone into the ship and then pull trash as quickly and safely as you can.
I have no idea how much time you have, but to me it seemed like we did the trash in about 4-5 minutes. It could have been longer or shorter, I unfortunately am not sure. Anyways, don't worry about the time limit and simply pull mobs quickly but safely. You really want to pull the Night Watch Mariner mobs (of which there will be three or four of) by themselves because they are huge pains in the ass with insane AoE and an annoying stun mechanic. If you pull a Night Watch Mariner with another pack of mobs, it may be best to wipe ASAP and immediately respawn. Be sure to focus the Helarjar Mistcallers, as they cast Whirlpool of Souls, which is an annoying AoE that damages the group and heals the mobs. You also want to avoid The Grimewalker mob, the large flesh giant walking around by himself.
You do not need to pull The Grimewalker and there's no reason to waste time with it. There's quite a bit of trash between Ymiron and Harbaron and you don't have a lot of time to do it, but because you don't need to down Harbaron himself for the achievement, do not be afraid to pop major DPS cooldowns such as Lust/Timewarp in order to blow down the trash quicker. Also remember, if you start to wipe it is absolutely a better idea to wipe quickly rather than screw around and struggle away precious seconds.
After Notes: It's a real pain in the ass that the game doesn't show you how much time you have, leaving it up to random speculation at this point, but as long as you have good group communication, pull mobs safely and burn them down quickly, then this shouldn't be much of a problem. The only real issue is is that, so far as I know, once the Captured Val'kyr is executed there is no way to reset the achievement for the week. This means if you fail, you fail for the week, which sucks if that's how it is. Consider trial-running the instance on Normal or Heroic so you can formulize a plan for the trash pulls. It'll be worth it, considering that failure means waiting for Tuesday just to try again.
POOR UNFORTUNATE SOULS;
"Defeat Helya in Maw of Souls while all group members are Poor Unfortunate Souls on Mythic difficulty"
I have not completed this achievement as of yet but from what I can tell, this may be one of the most difficult things in the game at the moment. How this works (from what I can gather, please correct me if I'm wrong) is that the group will need to travel to the Black Rook Hold dungeon. In the first room of the dungeon there is a fire burning in a brazier that you can click. Clicking it will give the group the Wandering Soul buff, which will last for 30 minutes. Now you need to, essentially, do every single Black Rook Hold boss (it might work on Normal/Heroic, I do not know) without dying. Each time you beat a boss (maybe?) you get a new buff that replaces the Wandering Soul buff/whatever buffs come after. Essentially, once you've downed all the bosses you will now have the Unfortunate Soul buff. Now you need to go back into Maw of Souls and defeated Helya. Without *anyone* dying once. I do not know if this is how the achievement works, we didn't attempt it this week, but more information will come on this after the reset. Like I said, if you have any additional information for this, please let me know.
---
As of right now (9/5/2016) this is all I have. I am typing this in the morning, and by the evening we will have done at least another 5-10 achievements, so this post will be updated by tomorrow at the latest. If the guide is any aid to you, remember to check back later for more information. I made this list in large part due to that fact that finding good information concerning these achievements is hard right now, and I wanted to help others out so they don't get stuck wondering what the hell to do when WoWHead provides nothing but a bunch of stupid HAHAHA I NO WAHT DIS ACHEVMENT REFERNCE U GUYS comments. Please give me whatever feedback you can so I can improve/expand the list. Thanks, and have a fun.
- - - Updated - - -
If this helped you at all, be sure to comment and leave some feedback, it'll help me shape this up as I work on writing out more of it.
- - - Updated - - -
The reddit post has been updated, I'll update this sometime later to reflect the changes.