I dont see the problem with Nasus. Hes shut down by just about any tank with CC, and he really only kills squishy targets, which he wont do until 30-40 minutes into the game.
The main issue with him is split pushing your towers down. How you guys are getting wrecked by him in teamfights is beyond my comprehension. If you are an ADC, you should have a QSS 40 minutes into the game when he finallly decides to join a team fight, to which you just QSS his slow, and run away from him or even kill him if you are farmed, which is far easier than you think when you arent withered.
Yea, if everyone on your team is a squishy assassin or carry, and you have low amounts of CC, hes going to shred your face. But one tanky member on your team with CC can completely shut him down in a team fight, which is why he's usually split pushing more than team fighthing. Nasus never gets LW, so if he is forced to beat on someone tanky, he doesnt do anything.
The problem is, people refuse to build defensive items, like QSS, or they play "carry" champs, to where if he manages to get on you, he can blow you up. Esp in my elo, I think in the last 100 games I'm the only person I've ever seen build a QSS. The only one. I recently 100-0 a farmed nasus as Caitlyn, and he never hit me once. I QSS'd wither, and proceeded to kite and murder him. I've been the tanky peel, and just spammed gragas barrels and taunts all over him and made him useless.
Really, if there is one thing you can cry about, its his ability to split push towers down and how annoying that is, but its probably less annoying than tryndamere or YI, imo.