Melee Swing -> Melee Swing + Break Application -> Double Attack -> Caustic Slime x2 -> Melee Swing -> Caustic Slime x2 -> Melee Swing + Break Application -> Caustic Slime x2 -> Massacre -> (Feud, maybe)
The exception mentioned above is the very first 30 second chunk. The melee attacks are sped up at the start, likely because of a combination of two reasons. An attack speed debuff isn't applied before the pull, and they changed the encounter a little in a hotfix which forced Chimaeron to reset his swing timer after a massacre. As such, the first rotation has time for an extra melee swing before the massacre, and that swing will always be a double attack. Also, the first rotation can't end in a feud. The first rotation, therefore, is:
Melee Swing -> Melee Swing + Break Application -> Double Attack -> Melee Swing -> Caustic Slime x2 -> Melee Swing + Break Application -> Caustic Slime x2 -> Double Attack -> Caustic Slime x2 -> Massacre
Feud phases work the same way as a normal phase on heroic mode with the exact same rotation except there's no invincible bot up and you're guaranteed to not get back-to-back feuds. An interesting thing that I didn't realize until I looked at the log is Chimaeron actually continues to spew out two Caustic Slimes during the feud phase, so the healing needed is double what I thought it was. Also of note, there's only ever one double attack during the feud. (He does cast it a second time at the end which is certainly scary but it gets cut off by the ending massacre. You may need to maintain your attack speed debuff to make this be true but you better do that anyway.)
So, how do we tank this? When it comes right down to it there are 4 different levels of melee attacks in the fight and 5 different levels of the break debuff and the trick is managing which of the attacks gets eaten by who has which level of debuff. On normal this rotation is pretty trivial since there's only 2 levels of melee attacks:
- Normal auto-attack which can't kill anyone at more than 10k health. Anyone with a taunt and a healer can tank this regardless of break stacks.
- Double attack. From the logs it looks like I get hit for about 140k from a base swing, with some variance. (140k is the high end.) You need to remain above 10k from the first swing to live through the second one with the bot buff, so if I have 150k health I'm fine. With 1 stack of break I need 185k health. With 2 stacks I need 220k health which I hope can be seen as clearly right out. I can cool-down that if I need to, but by default I'm dead if I don't avoid one of the swings.
On heroic things get a lot trickier. You have two new classes of attacks to look at:
- No-bot auto-attack. These hit for 140k, and there are 4 of them to eat. The second one applies a break debuff, so if you're planning on having one tank eat them all you'll be taking a couple of 175k swings as well.
- No-bot double attack. Even without a break stack you have 280k potential incoming damage so you need to use at least one cool-down here. If you have one break (likely since it was applied not 5 seconds earlier) you have 350k incoming. 2 stacks is 420k. Yikes!
The rotation we were working with last time and will probably keep going forward is to use a plate DPSer (ret paladin in our case) as the 'main tank'. He eats all the normal auto-attacks and therefore also eats all the non-feud breaks. 'Off-tank 1' (OT1) taunts in to eat all the normal double attacks until the first feud. These are all 0-break botted double attacks so there's no need to use any cooldowns of any kind. During the first feud he takes all 5 hits. This requires using at least a powerful cooldown for the double attack since it's 350k incoming damage and probably using a cooldown for the other hits too if possible. (As a blood Death Knight I can use bone armour for the entire phase for a 20% reduction and icebound fortitude for the double attack for an extra 50% reduction which actually lasts 18 seconds so will hit a couple normal swings too.) Then once the feud phase is over OT1 does nothing else since he has a 2-break. His job is completely replaced by a second tank filling the exact same role. This new tank (OT2) will taunt in for normal double attacks and will tank the second feud phase in its entirety. Note that even if the feud phases come as fast as they can OT2 will be filling the off-tank role for at least a minute and therefore OT1 will have dropped his break stack by the time the second feud has ended. This means he can easily step in and tank double attacks after the second feud phase, restarting the cycle.
The only potential problem here is OT1 may have to tank a feud phase 2 minutes after he last tanked one. Icebound fortitude has a 3 minute cooldown and therefore won't be up. I'll need to use vampiric blood, dancing rune weapon, and the hoping defense to survive. (Possibly get an external cooldown from someone else as well.) I should still have bones on the bone armor, so I should have 20% damage reduction and 15% more health. So I'll be at 222k max health and prevent 20% of the incoming 350k damage. So I'm dead by 58k. Oddly enough, if I got hit by the last melee attack I should have a large enough blood shield to live through this! Probably I should also pop my darkmoon faire trinket for an extra 10k health to make sure the blood shield is good enough...
You can also use the same rotation with a third tank instead of a plate DPSer but this doesn't seem to have a lot of merit. The main tank just screws around with a 4-break stack the whole fight so he's useless at stepping in and doing anything else. Possibly you could run it with no set main tank, and have the old feud tank become the new main tank. This would let you refresh the cooldowns on 3 different tanks for the feud phases which could be important, but would cost you a DPSer during the final burn phase. It does gain you a third speed bump in the burn phase, too, which may be worthwhile. I'll find out when we actually make it to phase 3.
I've also heard it done with 2 tanks. In this case you end up just holding on to the boss after a feud phase until the other tank's break stack drops, which often entails eating normal 3-break double attacks which is pretty sketchy. The guy who claimed to do it this way was the one with the Ardent Defender/Guardian Spirit rotation which makes me think it's doable with the right composition but that it's not worth looking into further for my purposes. We have a ret paladin and a DPS DK who can fill the 'main tank' role here without losing all that much damage in the process.