Did you try Stun Arrows once his health gets down some? Poison Arrows also has a brief stunning effect. At least in Broken Valley both skills can be found as bonuses on jewelry.
Once you get (the other) Raze's hit points down, did you try hitting one of the levers near the regeneration chambers to temporarily deactivate that one? A build-up of summoned armours and your creature can also sometimes block his access to the chamber. You should be able to finish him off if he tries to run for the far chamber.
General Raze how defeated? (D2:ED topic, but AFAIK it is the same in DKS/FoV)
If you have a save before entering the headquarters, you could also just move on and clear more of the fjords or the next flying fortress, and go back for Raze when you are a higher level or have a better bow.
