As not everyone knows I've been poking around on the PTR with the LFR tool which has given me some nice experience with this bugger, I will now share my tactics on this bugger for the 25man normal mode.
The mechanics of the fight are fairly easy and I think that the only thing that would wipe us are the numbers. either the raid damage gets too high or we can't get the slimes down fast enough.
It requires 2 tanks and 5 to 6 healers. It's doable with 1 tank but that tank and the healers better be amazing when trying it with 1!
Anyway, for the slimes (It's in a nice picture copy pasta'd from wowhead):
The slimes spawn from colour coded pannels at the back of the room and before the slimes spawn it tells us which slimes the boss is summoning.
Purple: Kill this at all times, it gives players a stacking debuff when healed either by a direct, aoe or hot heal. This is counterproductive and makes healing impossible. at 5 stacks it will blow you up as with the seeds at majordomo and causes everyone in the raid to get 55k shadow damage.
Green: The green is the only one that requires us to spread (4 yard range), this has to be the second on the priority since the other two slimes will most likely force us to stack up. stacking up and spreading at the same time is impossible so kill the green if the purple is absent.
Yellow: As seen by the picture it makes void bolt a raid wide attack. The debuff is only applied to the person tanking tho. we want to stay stacked up for this. Yellow is 3rd on the kill priority since it decreases Yor'sahj's ability cooldowns by 50%.
Red: It gives random players (I believe 8 in 25m) a debuff that deals more damage the further away you are from the boss. everyone needs to be stacked up behind the boss because we don't know who will get the debuff.
Blue: IMPORTANT FOR ALL MANA USERS! All your mana will be drained as soon as the blue slime reaches the boss. SAVE ALL YOUR MANA REGAINING ABILITIES FOR WHEN YOUR MANA IS DRAINED! (As stated in the video.) When your mana is drained it will spawn an add called "Mana void", every single magic user (Except warlocks if they feel comfortable) need to stay in 30 yards range of the mana void. When it's killed it will redistribute all the stolen mana to every magic user in the 30 yard range.
Black: Stack up and AoE the adds down, they can't be tanked.
I know it seems like a lot, but just remember to always stay stacked up unless you need to chase a slime or when the green slime reached the boss.
This is basically all that there is to it. ranged can stay stacked up at all times but melee sometimes need to move around to kill the mana void, maybe we will do good with assigning two healers to stay with the melee.
