It isn't about weapons being the strongest, as the only difference is the range in damage that they deal. Weapons with a large damage range can deal very high damage, but at the same time, very low damage (some weapons have a damage range that is large enough to deal zero damage!). A lot of nulgath items have a large damage range, like the hex blade or the iron scythe of nulgath
It's enhancements that make you more powerful. If you want to be able to deal more damage, perhaps you should change your enhancements, though I don't know about enhancements for battlemage. But one thing I'm going to say is that you should not use all luck for necromancer, my individual testing gives me a good reason to say so.