This is a really good post. Instead of posting my own I'm gonna respond to this one:
The thing with Yasuo is his ability to scale massively with skill level and too be honest you don't really need all that much skill to be good with him, im not putting Yasuo mains down because there is a good amount of skill required but you dont need to be diamond level. Its the same issue with Lee but way worse, Lee is "hard" to play (although as long as you hit your abilities you can kill almost anyone thanks to his ridiculous base damage, tank, and survive-ability) but once you reach a certain amount of skill and mechanical ability, he is incredibly strong and versatile. Yasuo takes that to the next level, his kit gives him the ability to out play about 99% of all situations with correct timing, knowledge of the game, and mechanical skill. Basically when played at maximum potential, Yasuo is untouchable, unescape-able, and unchase-able all with the ability to deal massive amounts of damage with just 1 item (shiv).
Yasuo is still exploitable, but you are pretty much right about everything else, especially Shiv's ridiculous synergy. In fact, the one biggest problem with Yasuo's balance is Statikk Shiv:
Q is supposed to have counterplay until you buy Attack Speed. That way, by the time teamfighting starts to become common, Yasuo's damage counterplay goes down in order to compensate for his squishy meleeness against a team. But the other thing about Q is that its base damage is quite low. This way, a Yasuo who rushes Attack Speed will not deal very much damage per Q, compensating for the fact that it's much easier to land. These things combined prevents Yasuo from becoming a monster before 2 items: an AD item and an AS item.
The problem is obvious. Shiv gives a lot of damage while also giving the AS to lower Q's dodgeability. An easy way to remove this synergy is to remove the much-hated double Crit passive. While I'm convinced that his build will switch to Black Cleaver + Tiamat like every other melee AD champion buys now, he still does have Crit scaling on his Q, which might be enough to make Crit items viable.
This means he is a well designed champion to be honest, so why is this such a bad thing? Well it puts him in a tier above most other champions. Take Brand, a very strong mage with good damage, great poke, decent waveclear, and good peel if you are skilled at using it correctly. But even if Brand is great at using his abilities and dodging, there are still a lot of things he cant deal with, such as targeted hard CC, long range poke such as AA's, and instant burst. Yasuo on the other hand can block any targeted hard CC that is a projectile, easily dodge all skillshot, block long range poke, and has an easy to gain shield in case he cant dodge or block certain damage. The biggest problems with this are what he gains and yet loses nothing for. His shield he gains just by moving, something that all champs do. His double crit passive he gives nothing for and with only 2500 suddenly almost half his attacks are dealing double damage. He gives nothing for these, what little he does give for the rest of his kit, he more than makes up for with Wind Wall and his Dash.
I feel Yasuo's power comes from one specific place: the inherent weakness of being melee. Yasuo is given so much in order to survive because he has to deal with very punishing positioning issues against mid laners designed to be weak due to their range such as Annie. Against such champions his play pattern is quite intense for both sides. But then you put him against someone like Vel'Koz and suddenly Yasuo is a problem, because his tools to fight low counterplay mid laners are ridiculously overkill against normal ones.
Yasuo needs to stop gaining so much for nothing, that double crit passive needs a harsher drawback because whatever drawbacks are there are clearly not apparent. The shield is too strong for how often he can have it up, most mages can not reliably poke him enough while its down due to mana restraints, meanwhile he has no resource. His ults drawback was suppose to be "oh it requires them to be knocked up" but he has a long range line knock-up or a large AoE knock-up depending on how he wants to play it both of which are capable of knocking up multiple people. Yes it is decently easy to dodge but then there are just so many champions with knock-ups almost any team comp will have sufficient amount of knock-up to proc his ult. He just has so much going for him and very little against him other than the players skill.
There's also the fact that he's a squishy melee sustained damage dealer.
There are two solutions:
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Nerf or Rework Yasuo so he is better matched to the overall power of his fellow champions giving him a better balance in what he gives to what he gains, probably the easier of the two solutions but then Yasuo might not see as much play since most people play him for his ability to curbstomp most people. This would need to be done to several other champions as well.
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Buff or Rework all other champions who are more balanced in how much they give for what they gain. Ultimately this will create balance through imbalance, but then this would turn this game even more into "who clicks the buttons faster!" and the amount of champions you would need to buff/rework is pretty massive.
The problem with these solutions is that neither addresses the real issue with Yasuo's design: he is made to fight low counterplay champions in order to not be shut down for losing champion select, but when put against a healthy champion is incredibly oppressive. This is not just a problem with Yasuo himself, but also with champions whose balance is 'my range is low'. Champions such as LeBlanc, Ahri, Jayce, Twisted Fate, Lissandra, I could go on, are designed just fine with other ranged champions in mind, and melee burst damage champions are still able to beat them with careful play, but sustained damage melee champions stand absolutely no chance whatsoever. Counterplay through low range is simply not something that works well nor does it feel good for anyone.
awhile back. But complaints about her has died down as every role gets more and more tools to deal with her, with them being optional so those who get stomped by her can learn from the experience.
and his E than physical. And that early into the game there really isn't an item that can be built to provide MR + Armor and an offensive boost to compete with his damage output. And even then he has so many defensive utilities (W, Shield, E to dodge) that it's nearly impossible to take an early lead on him. His kit is designed to serve as an AD Anti Mage, but is applicable in nearly every situation and synergizes amazingly with any AoE knock up champ.
who are encouraged to not interact with you, have kits that are larely impossible to outplay when used correctly, and just beat you to death with their ball of stats. I don't find Yasuo frustrating to play against unless the matchup is literally unwinnable for me, and very few of those unwinnable matchups exist despite what people think. I've never enjoyed playing against a Cho or Shen.
ult is blocked a bit, but not more than half then what the wall blocks is removed, but not the entire thing. Maybe more than half and the entire thing is gone? That and something where aerial things like 
