I am just going to assume that we'll be doing Hellfire Citadel on normal to complete these as most will be alot easier with our damage output and gearing at this point.
Hellfire Assault: Nearly Indestructable
Basically, we all need to focus the tanks (Fellfire Crushers and Artillery) as priority. The biggest machines to be aware of is the two that break through either side, which are the third one (left side) and sixth one (right side).
Ultimatelly, one of the easiest achievements to get.
Iron Reaver: Turning the Tide
There are two sets of mobs which spawn to the south and north on high platforms when this fight begins. The boss and raid needs to be positioned in a way that Barrage hits these groups. Which means the boss has to be close to the wall and ALL RAID MEMBERS need to be where we want the boss to be facing to fire the barrage.
If we use this image
we can do it using 4 barrages, and one air phase. Skull is boss positioning, and the adds are the X and Square markers.
Kormrok: Waves Come Crashing Down All around
I believe we all have this achievement, but it's about killing the boss and avoiding the purple waves he spawns. Really simple to achieve and boss will probably die on normal before he does these.
Hellfire Council: Don't Fear the Reaper
The only thing that makes this harder then an even dps burn is that at 30% hp, each one gains an additional ability...so you now will have all three of them happening at once, also Gurtogg's Tainted Blood (his new ability) he will keep casting until he dies.
Effectively meaning the whole raid will be losing 10% of their health pool per stack of Gurtogg's ability, half of the raid taking damage from Mark of the Necromancer dot (or more if you get dispel happy...), and taking damage from Jubei'thos' Wicked Strike (increasing over time as well).
Burn Gurtogg/Jubei'thos/Dia to around 32% collectively. Wait for Jubei'thos to finish a Windwalk (mirror images), then use lust and burn all three down evenly (you can assign dps, or call to swap, depends on what is best for your group). Just be sure that none of them die, until they all are about too.
The end of this fight is a dps race, also major healing CDs should be used shortly after the three have pushed sub 30% to ensure the raid does not die due to the damage.
Kilrogg Deadeye: A Race Against Slime
Again, an achievement we should all have. On normal, even easier, defeat Kilrogg before Ariok dies. Simple.
Gorefiend: Get In My Belly!
This achievement needs to be completed during the feast phase of the fight. We need two DPS without the Gorefiends Corruption debuff (basically not gone into his belly pre-feast) to die during the feast phase (jump into the puddle he is in) and kill the three Fragments of the Crone inside the belly.
This will make the Soul of the Crone appear outside, which then needs to be tanked and killed.
Shadow Lord Iskar: Pro Toss
The Eye of Anzu can NOT be on any given player for more than 5 seconds. Which means the tank/healer who are throwing it and any raid member who gets it during debuffs must prioritise the movement of the eye over anything else. The trouble period being the 3 add phases, but we should be able to negate the phantasmal bombs by being spread out.
Socrethar the Eternal: I'm a Soul Man
What you want to do is have the person taking the construct to place the first Fel Prison slightly away from the portal. This allows for some room for later waves of ghosts spawning to walk into the prison.
You want to do this because ghost spawning timers are sometimes slightly off.
After the first wave of ghosts has been successfully imprisoned, keep a freezing trap active on top of the ghost portal at all times to slow them down slightly as they spawn. Try and avoid using the Constructs Charge, as this can slow too much and sometimes only trap half the ghosts because others are trailing behind.
As waves spawn, you want to place new prisons on top of the old ones the moment the new wave spawns at the portal, thus effectively trapping the first wave again in conjunction with the second wave. Druids can help pushing non-imprisoned ghosts backwards if they run out of range before the prison triggers, though freezing traps should suffice. You can also use Death Knight AoE Grips to stack imprisoned ghosts tighter if they are a bit spread. The goal is to have all 20+ ghosts trapped in one prison by the end which is easily achievable.
The raid should be stacked somewhere so all ghosts run in a straight line. People getting Gift of Man'ari move in front or behind the group while still staying in the line.
Each Ghost wave consists of 6 Ghosts and there are 4 waves spawning before the portals switch positions. So you can have a total of 4 ghosts escaping.
Once you have the 20+ ghosts trapped, simply wait for the last prison to time out, this will release all ghosts at once and you don't need to worry about killing prisons. Since portals change location, have your construct player simply deal with the ghosts from the new portal while waiting for the old one to time out.
Raid should still be stacked up so that once the ghosts escape they don't run all over the place and melee don't go near them! This is important, as anyone getting hit by a ghost will kill it, but not give you any credit.
When the ghosts come running, pop heroism, keep them slowed and stunned and AoE them down.
Fel Lord Zakuun: This Land Was Green and Good Until...
Basically, don't soak pillar spawns. Means everyone needs to be aware of soaking the waves instead. Relatively simple on normal mode.
Xhul'horac: You Gotta Keep 'em Seperated
Do this as we do, but don't clear any patches. Which means more focus on imps to stop them casting extra orbs while on purple side and in the middle.
Tyrant Velhari: Non-Lethal Enforcer
We have to keep the first add alive throughout the entire encounter. Does extra raid wide damage. Trivialized by bringing an extra tank and off tanking to the side of the room.
Mannoroth: Bad Manner(oth)
The doom lord in question comes from the curse of the legion that is active in phase 1 of the encounter being removed/falling off naturally. This debuff is activated by the Fel Iron Summoner at the RED Fel Spire (the other two being the Purple, which spawns imps, and the green, which spawns infernals). The best course of action is to kill the red spire add right away to only have to spawn the one doom lord which must remain alive until the final phase of the encounter at 35% health remaining on Mannoroth. You can ONLY get the doom lord in phase 1 from the red spire add as Gul'dan destroys the spire going into phase 2 (unless doing the fight on mythic, but you'd not want to be doing this achievement during the mythic fight)
Given that the doom lord has the Mark of Doom ability on it, all raid members will need to watch for it as they must take some damage when they receive it to make it explode on them (letting it expire naturally is an insta-kill). The easiest, but most healing intensive, way to let this happen is to let one of the Shadowbolt Volleys from the doom lord go off on the raid, detonating all of the marks at the same time (do not be stacked up when this happens). Another way to do this up until 35% is to run into the fire of an infernal, as infernals will be part of the encounter as well until the final phase. This lessens the burden on the rest of the raid and likely ensures you won't be blowing up on anyone else.
When you get to the last phase, the order of abilities that you'll likely see is the cast of Empowered Fel Hellstorm, then Shadowforce/Gaze, and lastly after some tank combos, the Fel Hellseeker will come out. If your raid is mostly stacked, this should be predictable in where it lands. The doom lord will need to be at sufficiently low health that the damage from the three bursts of the hellseeker (by having whichever tank is holding it move into the circles intentionally) will be the killing blow on the doom lord. Once this happens, it's safe to kill the boss (but have the achievement tracked as it will likely change colors when it is met)
Archimonde: Echoes of Doomfire
The achievement description is fairly misleading if not flat out wrong. To the best of our knowledge the only thing that matters is the time since the last of allure of flames. Allure of flames stops after the 40% transition into phase 3. Essentially you have 120 seconds from the last Allure of flames to kill the boss. We tried a few other options like killing the doomfire spirit @ 25% ensuring active doomfire on the ground @ archimonde's death and did not receive the achievement. Although we did not try leaving the spirit up for the entire encounter.
Essentially only two conditions need to be met. 1) Wait for Allure before going bellow 40% and 2) Do a lot of DPS sub 40%. Other than those 2 conditions you shouldn't need to alter your normal archimonde strategy significantly. i.e. feel free to kill doomfire spirits normally etc.
So, essentially two options here. Not sure what group DPS is like from 40% to 0, so that'll depend on which tactic we use here.