Nasus is just fucking unhealthy to the game. Even the people on this thread defending him as a champion concept, he sounds like Farmville simulator and in a much much more toxic way then any of the other stack champions.
-So... he never helps in team fights and spends his entire time on an island farming and split pushing.
-By late game he's practically unkillable and two shots towers with no counter play.
-By early game he has sustain with his Q making harass negligible, especially since harassing pushes him to tower, which is Nasus's favourite spot
-Pushing him to tower is Nasus's favourite spot because he has a ridiculous crippling slow that makes even 2 v 1 tower dives futile against him, not to mention his ultimate.
-He can also use this crippling slow to ensure ganks on your over extended lane (and yes, you will always be over extended when fighting nasus.)
-Nasus is slow but thanks to the godly new teleport summoner spell meta, he will either never be -not- in lane or he can deep strike onto a dragon contested area or something and wipe out the team singlehandedly like a squad of terminators.
IMO he is broken with no counter play if the Nasus knows a basic silver III skill: Last hitting
If anything, they need to nerf his sustain.