Someone mentioned in an other thread that he did this instance with 4dks and a pally. I followed up on that and managed to clear it myself with the dks specced blood and in blood presence. All of my characters are wearing full pvp gear, no pve pieces average ilevel 354.

Pistol barrage is extremely easy to avoid, have all of your toons stand on top of the tank while your healer is behind the boss. As soon as he starts casting pistol barrage spam follow on the healer and have your toons move forward just behind the boss and continue happily spamming dps. Sometimes the boss goes nuts and turns around and fires the last barrage into the raid but that's fine, just top everyone off. It helps to put beacon on the guy that gets the curse... pallys can't dispel curses unfortunately.