[shift244]

I find that the most annoying thing in the fight is that you're totally surrounded. One of the better things to do might be to make use of Ammon to help in the battle and clear out most of those things coming from behind. A few well placed mass area effect spells tend to work well. When the fighters are engaged with the golems, either Ammon (or Zjehavie I believe) can actually use the incantation on the reaver, so use who ever is more available before engaging it at all.

Depending on party makeup and play style, you may want to start incantating early, and defend the incanter, or you might want to clear out most/all but the reaver and then have the party be more able to distract/focus on the reaver while the incanter does his thing.