Has anyone managed to kill him on Inferno since the patch?
As a Barbarian, I cannot stand in the gas clouds for more than a couple of seconds (could just be gear) and he will spawn two new ones (one on himself and one of myself) as soon as he walks over the previous ones, therefore making it impossible not to avoid the gas and attack him at the same time. Eventually, he will fill up every open spot in the entire room. I've tried kiting him around the edges of the room, even adding in a C-shaped path through the middle area once I make a complete circle, and the gas will just not dissipate fast enough to allow for a second round.
Edit, as of 3 days later:
Here's for all of you Barbarians who don't have that great of gear and aren't millionaires: