Durza is an odd fellow, working more as a support than providing much damage himself. His basic attack may provide some single-target damage, but is more of a slow and a self-speed boost. What his ultimate provides instead of damage is an attack speed boost for his allies, as well as a damage increase and some enemy vulnerability at the cost of their health; however, with the Chaotic faction, that is another buff.  All in all, Durza has limited usage, but is a powerful Chaotic support.