Propably this spell isn't working correctly:
http://forum.wowcircle.com/showthread.php?t=352295
I think most spells have lower DMG, when you're using dual wield - maybe game doesn't count that you have second weapon equipped. With two handed weapon it should be working correctly.
You should test it.
Sorry for english
PS: Check it on other russian private server P****WoW. It's fixed. There's a thread on their forum with this same bug report and tests. Maybe it helps.
