Nasus is actually solidly below a 50% win rate, and has been for a long time. I think he definitely needs the tweaks they're giving him, especially as they're making sure they're windowed into his ultimate rather than just providing a cooldown increase in general.
Now, he DEFINITELY can be oppressive against certain team compositions, and he's especially dangerous if you don't know how to play against him. But, in terms of overall balance, he's actually a bit weak. He falls hard to any serious kiting, needs to stay in lane a long time (potentially losing his team valuable objectives in the early and mid games), and really only comes into his own if he's managed to hold the lane against ganks and early aggression AND managed to farm consistently until the 25+ minute mark.
That said, in the future this sort of thread is a better fit for Gameplay, since it's not actually a creation of yours.