Utior needs something added to his kit, like a heal on his ulti and make def up II last even after resurrection.
Drizz't needs something like an atk penalty II on his ultimate, which would give people more options in ice element. There's only one accessible atk penalty champ and it's gulal who has like a tiny aoe range. If you need atk penalty in ice.
Talwer needs a rework or something added to his kit definitely.
Hochadir is another underperformer I think. Either make his frost application better / wider or give him better tank stats with some kind of tank steroid in his kit.
Those are just a few off the top of my head. In terms of nerfing champs, it's a dangerous thing to do in a game like this. There are some champs that stand out in certain places like oggok / zeffi combo making team unkillable, or elecebre / lucien in arena, or felosia / phaessa / acilia / garius / gillian / mithrasea stall team comps in arena and stuff like that. I think there can be ways to address their power imbalance by changing the game mechanics rather than just nerfing champions.