Just because it has a high cooldown and doesnt block non projectile attacks doesn't mean its not OP. Thats like saying that Lux's ult isnt OP because if you're quick you can step out of the way of it.
Yasuo's windwall blocks projectiles. It says that in the spell. It is broken that it blocks all of Nami's wave if it hits a single bit of it, not to mention that it blocks from all sides, so positioning hardly matters. Just stand in it and youre free.
Shen has a much worse shield, where he blocks all incoming damage.
Shen's shield only defends against auto attacks.
Yasuo is a very high-difficulty champion.
First of all, that must be a joke. It took me, and most others just a few games (1-2) to get a grasp on him. I got my second penta with him and i didn't even have runes or masteries with him. I hardly play ad champs and it was my second game as him. They may have been a bad enemy team, but that's no excuse.
Take his squishiness along with the timing required for him to stay alive and make kills, he is fine.
Timing = land 3 Qs and ult as well as e on every minion to show your true mechanics of skill and mastery with him as you dodge every ability.
Not to mention you get to block 90% of the damage from the next incoming attack (if its above a certain point, else its all of the damage).
His passive is not 'overloaded', either.
passive shield (mentioned above), double crit (slightly reduced but that is nearly insignificant). Did I mention his windwall?
All you have to do is aa him ONCE, and then his shield is triggered.
What do you do if you're melee? His shield also makes a temporary shield that stops other damage if it was under that finite amount to pop the shield.
Lastly, it's not that I don't know how to deal with him. It's that if you have to change your play-style completely to match a certain champion, something is wrong.