I'm not exactly sure if this is a bug or a feature, but anyways.
In Karnor's Castle some of the spectral callers wield a 2handed staff (a ranger staff I think it was), which seems to override the generally lowered dmg bonus mobs get. They'll hit for ~110 dmg a pop, and just as fast as if wielding 1handers or nothing. It's not a huge issue, but more of a surprise that keeps it interesting.