So it's no secret that most players really don't like having to fight Yasuo. Even before the OP tank build and weird bug that gave him a 56% winrate, he was regarded as one of the most frustrating champions in the game by many players. A large part of that frustration comes from Yasuo's W, Wind Wall, which according to his champion page, Yasuo "creates a moving wall that blocks all enemy projectiles for 4 seconds". I'm sure most of you know this, but for the sake of clarity, this is the spell I'm referring to.
Now, there are many strange interactions created with Wind Wall, including a bug a while back where it would block TF's gold card, but Yasuo would still be stunned. Some interactions, however, are considered by Riot to be intentional. When Yasuo casts his W, the Wall itself spawns infront of where he is aiming, yet for the first few frames, the hitbox of the spell covers Yasuo's hitbox. This means that when Yasuo casts Wind Wall at just the right moment, he can negate a projectile that comes from any direction, even the exact opposite of the side the Wall is facing. Even though the animation clearly shows the Wall not appearing until around .125 seconds into the animation, its effects take place instantly. **_That's where the potential nerf comes in._**
I propose that Wind Wall's effect be brought in line with the animation. That is, that the spell should be made to not block projectiles that land on Yasuo within .125 seconds of him pressing W. As the actual Wall itself is not yet on the screen. It makes no sense for it to still stop your projectile, and this leads to a lot of very frustrating moments for those facing Yasuo.
I remember one game in particular that I was playing Twisted Fate, when I caught Yasuo at low HP, with his W having already been used. I threw out my gold card, and _AS IT IMPACTED WITH HIS BODY_, Yasuo's W came off cooldown and he used it, cancelling the card and leading to my death. Both myself and that Yasuo player agreed that he should have died, and simply shrugged the experience off. I hadn't even remembered that until a much more recent game where I played Lux, and a similar thing happened with my Light Binding being blocked within milliseconds of hitting Yasuo's hitbox.
TL;DR: Make Yasuo's Wind Wall's effect of blocking projectiles not take place until the animation of the Wall is actually visible.