I just did this last night, took me 2 failed attempts but here is what I did.
Dps him and his adds till I got 4 stacks of the debuff, then I ran around doing nothing but avoiding him while Mako cc'd and smacked him around. When he spawned the adds I still los''d him and killed the adds quickly.
The 4 stack of debuff will come off slowly but they will drop off.....then give yourself a big heal and dps him some more. In the end Mako finished him off while I was running around avoid him.
I still cannot believe after all that crap and the beating she took from him and adds that she gave me a -30 aff for putting a bullet in his head.