I think it´s obvious a champion needs help if his winrate is about 40%, which is the lowest of all champions in League of Legends by the way, for many patches (as you can check at op.gg or similar websites).
I know not many people play Nunu but some do! For example me. He was one of my most successful champions in s7 (reached Master with him) and it´s sad that he is as far away from "viable" as he could possibly be.
I mean even other unpopular champions like Skarner or Heimerdinger were considered in Patch 8.1 but not him.
So i beg Riot to buff him so he can be played again even in higher elo (dia+).