Yasuo is a .... I will call him a noob tube as a reference from call of duty in his current state. There are very few mid champions that can really stand to his lane bully stage, however he never falls off. His mid game is insane and there are plenty of ways to build a comp around him so his Q isn't the issue.
You do not want to destroy what Yasuo does in lane either. The nerfs to his Q was correct and now people play him by maxing the E. Which is great and I approve.
What needs to go in his kit are 1 or maybe 2 things.
1. Wind Wall has to have a breaking point or thresh hold. Either takes 3 AA to break it or stops up to 2 spells before breaking.
2. Change his resolve from the passive to give him % Life Steal on next AA or something other than a built in shield.
Personally I think if the Resolve (#2) is the best area to address this champion. Right now, it takes 1 AA to pop the shield. Not only does it pop the shield but also he takes 0 damage. It is very powerful in lane phase pre 6 and is an issue really. From Bronze to Diamond, this is by far the most difficult thing I have seen mid champions have to deal with when playing against Yasuo. He maybe has caused the most rage for lower skilled players than any champion currently.
I really do not think we need to address his damage, he is an assassin champion, but taking away his early tanky might be the best way to end his rein of terror in mid. Because of comps, his skill level is very lower and I do not think the developers thought about this when he was developed. On paper he worked, but in game, he has caused too much issues. It is OK to be a lane bully, but when the best way to counter him is to play very passive or have jungle camp, that is not healthy. Can some mid champions do well vs him? Of course, but that still doesn't mean he doesn't need a tweak. I think tweaking his passive in the Resolve is the overall best solution.
TL/DR: Change Yasuo Resolve to something other than a shield in order to promote healthy counter to his lane phase regarding to middle lane.