I had difficulties first time I encountered him, because our group panicked when he does his missile spam move; everyone ran around like crazy, healer coudn't heal and the explosions hit everyone.
Im a sage healer, and that is exactly my biggest problem in that fight. It is so much easier to heal if people just spread out a bit (staying in range for the AoE heal) and stand still. There is no need to run around as headless chickens.
As long as people stands still and makes sure to interrupt his headshot ability, the fight is actually not that bad.