You probably already know this, but just in case... A lot of it is basic raid stuff that I'd mostly forgotten after trouncing around, overpowering everything hehe. Doz made me remember a few things, including how much of a pain it is to do the 'basic' raid stuff when you're boxing a full group hehe :)
Corner tank him and make sure your healer is around the corner out of the ae.
Don't let your casters get hit by the ae.
Keep your clickies up.
Make sure slow lands asap and doesn't fade.
Don't forget that belly casters exist!
If you can manage to do all that and still can't kill him, then you just need more levels/gear.