Nasus may not be OP, but he is completely un-fun to lane against.

Going against a Nasus in lane is just brutal, god forbid you chose a top laner with mana! If you do you're screwed, he will just sustain until you're out of mana and you either back or stay and watch him as he farms. I'm not saying he is OP by any means because he can be kited to hell and back. I'm just saying that when he's your lane opponent....it just plain sucks no matter what, it's not fun by any means. I'd rather go against a Riven or a Darius, at least it gives some excitement to the lane.