The biggest issue Nasus faces is that he never truly feels tanky

Which is really strange when you consider his ult now. But for various reasons, Nasus never gets to a point where he feels like he's downright difficult to kill. Sure, in 1v1s he's tanky and that's nice but it does nothing to help him where he needs help most. As a split pusher, he takes a long time to scale and his split push is incredibly binary. Either he can 1v2/3 or he can't and if he can't, his split push is not threatening. In fact, at that point, he's just farming.

That was one of the great things about Nasus back in the day. If you didn't do too hot in lane, you could build up and be a front liner for your team. But he simply doesn't do that well anymore and while I could debate those reasons for eons, that's the simple truth. At this point, I really believe it's time to introduce Nasus to % damage reduction somewhere. The resists on his ult are nice but by the time they give him meaningful values, his ults almost over and he's almost dead or it's late game where he's not tanky anymore anyway. At least with %damage reduction, Nasus maintains durability at all points in the game and isn't designated to a cheap one trick pony split pusher, one of the most unhealthy split pushers in the game.

I would totally take compensation nerfs on his Q (like hitting towers with his Q doesn't reset its cooldown) if he could get meaningful teamfight buffs.