I just did this instance for a while and we wiped plenty of times on the first boss. It is quite insane on how hard this boss is. What was killing my group is the plasma arc, it spawns it to much for DPS and the healer to actualyl do anything constructive, without running around headless.
Ontop of that you got lava bursts and Adds and Incinerate. As a BH tank I noticed that the plasma arc hurts a lot, even if you touch it lightly. Without the amount of spam around it, makes it really hard. which to say is, I got to watch out for those while I dodge lava bursts from the floor, try to grab adds for the dps and also interrupt incinerate? Which if i miss it, pretty much nukes me to hell and back.
Just lower the amount of usage of Plasma Arc and the encounter will be fine and fun.