Hello guys, my guild wiped on Heroic Immerseus for 3 hours last night with little progression. After numerous guilds and guides telling us this boss is "very easy," "way easier than Garrosh normal," and "totally faceroll," I have been able to find little helpful information outside of the Scrubbusters Warlock strategy guide (I forget his name), and even that doesn't get very specific.
Raid comp is:
-Prot Warrior (MW monk alt)
-Blood DK (Prot pally alt, thought probably not geared enough to tank this)
-POSSIBLY Brewmaster tank, if they can cheese adds Tortos style or any other mechanic we can probably convince him to come in.
-Disc Priest (Pulls highest dps out of everyone in our raid in his shadow OS as well, with the exception of the other spriest and occasionally the hunter)
-Warlock (plays all 3 specs very well)
-Fire Mage x2 (one is usually much higher dps than the others but both have a tendency to stand in the puddles a little much)
Our issues are hard to pinpoint (I don't have logs unfortunately, I know that would help a ton), as we sometimes have a flawless phase 1 and then die at the end of phase 2, and other times all randomly die 15 seconds in.
We are popping hero on the pull and then going to 4/5 stacks before stopping and killing adds, then refocusing boss as soon as stacks drop. Our first few attempts had adds EVERYWHERE and there was just no way for me to pick them up without Mocking Banner (and the cd on it is too long to use it every Swelling Corruption), so we had our HPal turn on Righteous Fury and marked her with a raid marker so i could simply go thunderclap on top of her to get them. However, our priests are still pulling stupid high threat on the adds and often pulling them off of her, taking up to 5 adds on them. Combined with Swirl and the inability to see any puddles (nameplates covering most of the screen qq) half the time, we are getting TONS of random deaths. A lot of guilds I saw just sat in Swirl and popped a raid cd and nobody died. This happens to us about 50% of the time, but sometimes someone will get gibbed with a 5 stack DoT + add melee + swirl.
As for positioning, we are starting in front with everyone except the tanks in a straight line facing the boss (one behind the other) and then moving to the left every time a puddle drops. This works great up until adds spawn, and then people get all kinds of out of place for whatever reason and we end up with puddles all over everyone. We have the Blood DK tanking on the pull, I taunt immediately after the tank cone attack, and grab an add or two to attack for rage while I have high stacks. This usually works okay, however on a few pulls whenever we did a taunt swap the boss would immediately spam his tank attack on the whole raid despite me being able to melee him from where I taunt (I'm guessing his hitbox is just slightly larger than his perceived "melee range" so when one of us taunts at the edge of his hitbox we are counted as out of range). Also, the adds are absolutely destroying their tank when we manage to pick all of them up at once.
Any advice? We are not getting to P2 frequently, and when we do it usually goes fine except for the pool randomly expanding to cover the whole room and instantly killing half the raid whenever even just one or two adds reach it.
Edit: Which healers should we have in for this fight? Our rdruid and the disc pull the most as far as I can see, but having the disc as shadow is a huge dps boost when we sit a lower dps for him.