In which we do a thing and try not to go insane.
958 Ilvl 79/80 points, standard raid talents, and Prydaz and Soul of the Netherlord.
This fight sort of hopes rng is in your favor and you get the dream first. It's pretty important.
So in this fight you do this cool thing where you do very little damage at the start so your pet can hold aggro. Very exciting gameplay!
You do this so that your pet can take damage for you while you do some passive damage via dots. Your pet will die around the time the first manifested corruption pops up which is great because a new infernal can taunt that and it will never lose aggro.
Keep it dotted and make sure the void is back on the boss for extra dps.
Honestly for the first few voidlings you should just take the insanity hit to avoid having to stop draining. Or don't your call. I tried kiting them and found it less than satisfactory.
Once you go insane pop all cds (you get them back) and go to town on him. Don't let your dots fall off adds at all costs.
You need to get him to at least P2 (3 is ideal) before you finish your first madness.
The reason being meteor does 5 million damage and 40 corruption so you get at most 2 of these before you go back into madness.
On the first one I dot the mobs with DL to help get my health back up, and postpone some sanity loss in addition to getting my wrath damage started.
On the 2nd I use my defensive and put some dots on a respawning mob to keep the buff rolling.
The key to this fight is Soul of the Netherlord as it allows you to keep SL and in the final madness allows your damage to scale to insane levels. I did 165 million damage to him in 20 seconds with it. I can not recommend it enough. Finished with .6 seconds on the clock before MC. Calculated.
If you're a pet class and he's almost dead dont' despair as it won't reset until your pet is dead. So if he's nearly dead make sure your pet is topped off (or get a fresh one) pop it's defensives and prey it can finish him off for you.
Whelp time to find another boss to kill now.