My approach was drinking one of the potions prior to the fight making me immune to one type of gas. Then I pull. Tank them with the back to the group - when Fry (or whatever his name is) spawns, kill him asap, then go back the the remaining. If you have a dedicated healer, you can heal through the clounds you're not immune to, but if you're less geared or dont have a dedicated healer, simply watch out for the clouds youre not immune to a strafe/walk out of them.