Going to need more details than this to be able to figure anything out.
-What are your skill levels (all of them)
-- are you human or elf
-Approximately what damage were you doing before
-What damage are you doing now
-How much SDI did you have on then and now
-You're sure you're not just experiencing the effects of the fact that it does Chaos damage?
... may be other things that'd be important that i'm not thinking of.