I just got to the balthazaar / nightsong fight, and was surprised to see that Balthazar was a 100% copy of my sorc's build.
Except for me all the mobs were poison immune so I couldnt use my OP cloudkill

Icestorms and Fireballs cleared it easy though.
I was like 'how dare u kill me with cloudkill and twinned ray of sickness, THATS MY BUILD !!!' :x