Nasus is fine... except
His q is ridiculous and needs to be reworked. Any semi-decent player can get massive stacks even when dying more than the other top laner. Once mid to late game rolls around a pure tank nasus can 1v1 anyone, and can often 1v2 or 1v3 people no problem. Tank's shouldn't be able to do this much damage, they shouldn't be able to out dps everyone else.