I was at ilvl 522 when I did it so it wasn't overly challenging but I managed to kill him right after he summoned the first doomguard so I never even came close to the second set of dogs. The one thing I had read that help a lot was that you can use charge much more often than just to interrupt his cataclysm. Lowers the damage you take and increases the damage he takes. Just get the timing down to make sure you still have the charge up for when he does cast cataclysm and the dude should melt.