Does anybody have any tips on defeating this guy? So far i've been DPSing him to get embers in beginning then enslaving the Pit Lord and using him. I use the charge on CD and in line with my Chaos Bolts for 100% extra damage, then i've been using breath for the imps (which doesn't seem to kill him). I've also been LoSing his Chaos Bolts using my gateway as transport.
Also if I log off while in the scenario do I have to do it all over again?