Spent a while bashing my head against that wall the other night as others can attest to (much complaining on TS *grin*)
Not sure it can be done as a group... but feel free to grab me if I am online.
major fight spoilers below.....
phase one - blur - just him, dodge x4, unload a clip into his face, repeat
phase two - cloak + decoy - hide up the far end of the room, force the decoys into a choke point, they go down fast, when you find the real one unload a clip, he will vanish and this cycle will repeat. Adds will spawn in the alcoves above - kill them or they will do a LOT of damage to you after ~10 seconds.
phase three - over power - this phase hurts, almost anything he throws at you will kill you in 1-2 shots, and the ground is treacherous. that is all I will say for now.