I have 3 problems with Yasuo, none of which are his passive (the only thing I don't like is that you can't get 100% Crit without wasting some Crit):
1: Shiv synergises way too well with him. Q is balanced around the fact that it needs both AD and AS to scale. Buying AS first removes the counterplay of the skill, which is something that's actually good overall due to melee champions gaining more counterplay as champions group up, as well as it being one of the main sources of his damage and the only way to activate his ult on his own. However an AS rush means that the skill hits like a wet noodle. On the other hand, buying AD first means that each Q hits hard, and requires less time spent near the enemy to deliver that damage. The ability is easy to dodge in this state.
This is a good balance between stats that is absolutely destroyed by Statikk Shiv. This gives the AS to reduce the skill's counterplay while the passive makes up for the lower damage quite considerably. Blade of the Ruined King also synergises very well but at least has its power reduced early on; Shiv scales with Crit, which Yasuo gets double, and movement, which Yasuo has tons of. I don't know how exactly this synergy could get nerfed, but it increases Yasuo's early game power and removes the interesting relationship AD and AS have on Q's scaling.
2: Yasuo is too slippery. I know that complaining that a squishy melee is too hard to kill is pretty silly, but he is incredibly unfun to play against as a skillshot reliant champion. Wind Wall, the flow shield, and E's dashing all have counterplay available, but all 3 of them together makes a frustrating experience. Yasuo has so much protection that actually hitting through to him is too difficult. I actually like Wind Wall (sort of, more on that later) as it is one of the few mechanics that hits ranged harder than melee (when most of the time its the opposite). E's dashing is really annoying as it punishes skill shots but not targeted damage, when skillshots already have plenty of counterplay available. I know that melee champions can't exactly dodge when they're in someone's face, but thanks to Q and W Yasuo already has an advantage over most melee champions. The Flow shield is supposed to help against basic attack damage. From Mages. When Yasuo can easily trade with them. Hate it.
I would like to see either the Flow shield be removed entirely or only apply to physical damage, or alternatively E's dash having a longer cooldown when used against minions. The Flow shield is just excess power Yasuo doesn't need, and the mobility reduction helps land skillshots more easily without making targeted damage more effective.
3: Wind Wall. Some consider it the unholy grail, but I think it's a great, unique ability that sets Yasuo apart from his peers. Its scaling is all wrong though. 26 seconds is too long for a level 1 cooldown. Just way too long. For a defining part of his kit, it shouldn't be this long. On the other hand, its duration is 3.75 seconds at all ranks. Why? The long duration is at its most painful early game. Reverse this; the cooldown should be 16 seconds at all ranks (what level 5 is right now) and the duration should be something like 1.5 / 2 / 2.5 / 3 / 3.5. Also keep the width the same across all levels. You're not gonna try and walk around it in lane; the lower duration makes it easier enough to deal with anyways.
I think that tackling these 3 things will bring him to a better spot. If he needs buffs afterward, sure, go ahead. I think that these are problems that will persist as long as he's played, and that despite all this Yasuo is still healthier than any other melee carry we have. We can do better though.
