While balance wise he seems to be middling (According to champion.gg, he has a low winrate, but it also indicates that he has a 54% win rate if the player playing him has 50 games of experience), he does have design issues in his extremely overbearing early game due to low cooldown, reliable hard CC mixed with quadruple passive...
The biggest reason he needs harsh nerfs is because of Yasuo syndrome. The guy feels so immensely overpowered in the laning phase and can escalate so excessively that he draws the attention of the absolute worst teamplayers in the game. The ones who engage 1v5, and then blame someone whose lane didn't go over well. They lash out at literally everyone on their team when they are botching their game.
Putting Yasuo down for a bit to let those kinds of players disperse and force them to learn to work as a team would be a very good thing.
If that can't be arranged, at least have Yasuo permabanned from blind pick games.