I have only fought Malistair by helping a friend so the best combo would have to be........ Keep Frost Gainting if you are Ice, or if you are fire keep Fire Dargoning, or if you are life just use anythinng and heal up, if you are Death then dont use death just use your secondary moves , if you are balance just keep Judgmenting, or if you are Myth just keep Orthurusing and if you are Storm then just keep Tritoning. And I hope this helps.
My wife and I defeated him last night. We are both necromancers. We laid a prism down, then 3 different feints (normal, tc, gear) and bladed. She hit first and one shot defeated him with a secondary school Centaur. We planned on just laying down prisms and then use bladed Wraith, but it was not needed.