Our raid comp was;
- Blood Dk
- Feral Bear Druid
- Holy Priest (me)
- Rest Druid
- Resto Shaman
- Fire Mage
- Affliction Warlock
- Feral Cat Druid
- Balance Druid
- Survival Hunter
Our average item score was about 352 (I have 351)
Because of how the nuke phase works, it's apparently alot better to use casters than melee for this fight (see further below for why this is). We had three melee and the nuke phase worked really well (no one died!). I think using four melee shouldn't be a big problem, so it might be that this warning is mainly aimed at people who are trying heroic modes. You also need a couple of people with good interrupts, but otherwise this fight feels like it's fairly forgiving for any raid setup.
AC consists of four bosses; fire, water, earth and wind. You will fight fire and water in phase one, wind and earth in phase two, and in the final phase the remaining hp of all the four bosses will be combined into one boss that has to be nuked down.
Phase 1 - Water and Fire
Water - Feludius
Hydrolance - Also called Ice Lance. Is interruptable, but generally only a problem when it is combined with other skills. You can let it go through until the bosses start doing their aoe, that is when you want someone to interrupt it because the aoe and the lance combined can kill a player.
Waterlogged - Every now and then Feludius will spout out balls of water, kind of like Rotface exploding goos. Unlike Rotface exploding goos these are avoidable though, but being hit by them isn't the end of the world. You will get a debuff that if it stays on will have the player freeze in place for 10 seconds, also dealing alot of damage. Everyone has to remove their debuff by walking into the fire streak made by the fire boss (see more about that below).
Glaciate - When Feludius screams something along the lines of "I will freeze the blood in your veins" he'll do Glaciate, a skill that does intense damage to anyone in melee range and freezes anyone affected by the Waterlogged debuff.
Heart of Ice - A dispellable debuff that deals increasing frost damage. People who get close to the one affected by this debuff will get a buff that make them deal more damage to the fire boss. Some people will have the player affected by this debuff run to anyone fighting the fire boss (which usually is melee, see below), but we just dispelled it asap and that worked well too. You have to evaluate your dps and see if you need this extra buff to get the bosses down enough.
Fire - Ignacious
Inferno Leap and Inferno Rush - Ignacious will jump towards a random ranged player and back to the tank, leaving a trail of fire. This is the fire in which you will have to remove the Waterlogged debuff. If your ranged group stands too close to the boss, he will not jump! In that case you won't get any flame trail and you won't have any means of removing the waterlogged debuff. Trust me when I say this is a very sad way to wipe on this fight. The leap does a knockback, so if a healer is targetted and knocked away from their healing target, or an interrupter from their interrupt target, make sure to say so for everyone else to be ready. Anyone can be jumped to as long as they're far enough away.
Aegis of Flame and Rising Flame - Every now and then Ignacious will use a shield on himself, absorbing 1 million damage. Once cast he will start doing a rather nasty aoe on the entire raid. At this point everyone has to target the shield and nuke it down to be able to interrupt the aoe asap, think about how the shield on the Twin Valkyrs worked in ToC, this is very similar. Getting this to work fast enough turned out to be one of the trickier things in this fight!
Flame Torrent - Just after you've interrupted the aoe damage he will cast Flame Torrent. It's a frontal cone attack which is unavoidable for the current target (the tank). The longer he gets to channel Rising Flame, the more damage Flame Torrent will do. If you let it channel too long it will one shot the tank (unless your raid is already dead because of all the aoe damage).
Burning Blood - Just as with the water boss, Ignacious will place a debuff on a random player that deals increasing fire damage. When players come close to the one affected they will get a buff that increases their damage done to the water boss. Yet again, we just dispelled it. If you feel like you need it you can have the affected player rush to the ones dpsing the frost boss (usually ranged, see below), but ideally you won't have to bother with this.
Because of the above mechanics you'll want to set melee on the fire boss and ranged on the frost boss. The water boss does a melee range aoe, and having the melee moving from it is an unecessary dps loss. Make sure to have someone who will interrupt the Hydrolance during the heavy aoe from the fire boss. Since all dps should be focused on dpsing the fire boss this means that interrupter will have to have the water boss as focus (or have the tank tanking the water boss do it). As soon as one of the bosses hits 25% hp, the next phase will begin. Making sure that they're equal in hp all the way down to 25% is the key to this fight, as any hp they have left will be combined for the final boss in the last phase.
Phase 2 - Air and Earth
Throughout the phase there will be at least one hurricane and one sinkhole moving around in the room. The hurricanes will get you airborne, and the sinkholes will get you grounded. For some of the skills the bosses do you have to be either airborn or grounded to avoid intense damage. Having someone calling out which one to be at all times helps alot on this phase. The hurricanes and sinkholes deal a small amount of damage, so try not to be hit by them unecessarily. Keeping track of them at all times is the key to this phase, since you want to get grounded/airborne as soon as possible when necessary, without accidentally slipping into the wrong one.
Air - Arion
Thundershock - Deals intense damage to anyone not grounded. Usually doesn't one shot players, but is an unecessary load on the healers and should be avoided as much as possible.
Lightning Rod and Chain Lightning - Arion will mark one player who will be attacked with Chain Lightning. Anyone close to this target will take loads of damage, so have the targetted player move away from the rest of the raid (but not out of range of healers of course).
Disperse and Lightning Blast - Every now and then Arion will disperse and move to another location in the room. Just after this he will blast whoever is tanking him for a big amount of damage. This is usually no trouble at all as long as the healers are ready for it.
Earth - Terrastra
Quake - Deals intense damage to anyone not airborne. Same as with Thundershock, it usually doesn't oneshot players.
Gravity Core - According to wowpedia this does "Applied on entering a Gravity Well (Sinkhole). Crushes an enemy with intense gravitational force, inflicting 10000 Physical damage every 2sec for 10 sec. While the target is affected, the gravitational field periodically hinders the movement and actions of nearby allies. " But I've never noticed it during a fight.
Harden Skin - Terrastra will ocassionally cast a shield upon himself that lowers his damage taken by alot. This is interruptable and should be. You could also let it be because dpsing through it will deal alot of damage to Terrastra, but it also increases his damage done so it's usually a better idea to just interrupt it.
Eruption - Spikes coming through the floor, dealing damage and knocking people into the air. Just avoid it.
Just as in phase 1, you want to keep the hp of the two bosses as close to eachother as possible. As soon as one of them hits 25% the third phase will begin. This phase ( ie second phase) is usually considered a regen phase, in which healers gets a small break from intense healing to regen mana enough to handle all the damage in the nuke phase that comes after. If people are good at avoiding damage healers can regen alot during this phase, and this too is a key to succeeding with this fight.
Lava Seed - Rains fireballs randomly across the room. Don't be hit by them and don't stand in them.
Liquid Ice - Is the main reason ranged are better on this boss than melee. EM will place an ice patch below himself that will grow and deal more and more damage as long as the boss stands in it. Having few melee who have to deal with this skill therefore make this fight alot easier to heal. A few melee can avoid it by running on his sides and dpsing.
Electric Instability - EM will cast chain lightnings at random players, which will jump to nearby players. Try to spread sensibly, ie so that you don't get too many people hit by chain lightnings without being too spread for aoe heals. This is another reason you don't want many melee, because if they have to stand too close they will kill eachother with the chain lightning.
Gravity Crush - Will bubble a random player, stunning them, lifting them into the air and drop them (but not high enough for a levitate to work). The target is stunned and takes damage equal to 120% of their max hp over 6 seconds. They need to be healed enough to survive the bubble and the fall, but not so much that the rest of the raid dies from lack of healing.
This is without a doubt the trickiest phase. Healing is alot easier with as few melee as possible, as mentioned above, but this is a minor issue in normals (as long as you don't have more melee than casters).
Yet again this is a fight where we'll mostly deal with aoe damage. In the first phase we have to be ready for some occasionally intense tank damage, and the fire boss aoe (have everyone stack up for it). In the second phase healing becomes rather easy as long as the one affected by the Lightning Rod debuff moves away from raid and everyone gets grounded/airborne when they have to. The real deal comes in the last phase, where you will hope that the dpsers can burn down the EM before the damage becomes too intense. After a while the damage becomes so high that there just won't be enough gcds to handle it, even if you still have plenty of mana (and mana shouldn't be a big problem if your raid knows how to move from fire). We had healers assigned to one tank each and one to raid, and that worked really well since the damage is about one third each (except in the last phase where it is mostly raid damage).