As mentioned above his enspells are tiered. He doesnt always start of with the same one.
His first tier is (in no particular order)
A. Blind
B. Paralyze
C. Silence
D. Poison
Once all 4 of those are up, not sure if it has to be on just one person for him to access the other or not.
E. Petrify
F. Virus
G. I think there is one more cant remeber.
His hate system is based off who doesnt have what enfeeble. So if you keep your tank clean he will continually go back to him for the most part.
Hes pretty easy with over 6 people. Just have everyone bring antidotes and echo drops even if they dont need them and it should be fine. PLDs with reprisal do very nice as tanks, so do geared RDMs.