There is currently a bug with Nasus Q where regardless of the CC applied to him you can't stop his Q from hitting you even if you say use Fiddle fear on him while he walking up to you with Q activated and he will be feared but continue to hit you with his Q, this also happens to Fizz in his Playful Trickster as well which will stop his regular auto attacks but not his Q.
CC doesn't interrupt spell casts and attacks. The only way to stop an attack or spell casts is via Death. Thus Death is the best form of CC in our game.
So when he was cc'd you could still hit you? was he moving to hit you or where you standing really close? Also when Nasus uses Q the effect will stay for a little in case that was what you misinterpreted.
I did some testing on this with a friend and even Fiora's Riposte doesn't block it, that blocks EVERYTHING.
