Maybe this will help some of you guys to get the concept ... we just called it a night. Having killed the lootmonster on the 3rd pull, we were "afraid" about horridon. Mostly because of this thread. We ended up killing him on our 4th pull. (The amazing tip blowing bl on the 3rd door is really what it made for us). Having said that -- this is 10 man 5/16 hc last tier. average ilvl 495.
Stay focused and it will fall over.