yasuo could get some love
From all the things that dont involve a rework i think that reversing the shield nerfs and attack speed scaling of his q would be the safest imo.
You made it almoust impossible for him to get to mid game without feeding or simply dropping the lane because he cant compete for it, even if he gets babysitted he needs to get 5k gold and his 2 core items to become an actual threat, which isnt possible in mentioned phase of the game.
As far as i played him i noticed 2 wrecking problems, yasuo cant survive the laning phase, and yasuo scales too slow and requires too big items to stand up on his own after jungler helps him, ofc you can jump around like mad and get that free dmg off but you will just push the lane and its still possible for you to lose the trade due to your short hp bar (yasuo deals sustained dmg so a bursty midlaner might just pulverize him before he does anything scary, and 90% of midlaners relies on burst).
When i look at hp nerf without taking the rest of his nerfs into account i actualy like it, it reduced the opressivness of his kit without hitting anything that describes him (he cant trade early just because his hp bar is too short, while late game his shield fills the gap), bah it even allows to increase the importance of shield managment because he cant take blows straight on his hp bar.
But as far as the hp nerf is effective and good in my opinion, the nerfs he recieved before are what makes him unable to do anything. Shield is nonexistant, he doesnt get it as often as he needs, and it cant block anything (mainly because it expires so fast). His q's cd doesnt scale with champion lvl enough, its the centre of his kit and he has very limited acces to it till he spends 5700 gold and i mean the full value of botrk and static (ofc we assume that he doesnt spam daggers like mad becuase it makes no sence), without both im 100% sure that you wont get below 2 sec cd on his q at lvl 18 .
The nerf broke him indeed, but i personaly think that he is in the best spot to expose his uniqueness, theme and overall ballance him.
recently. I think he is really fun! But along with what you say he is to weak during the laning phase.
For example:
One of my recent games I was against a cho top (I like playing Yas top) and I was feeding not gonna lie, our udyr ganked twice died both times. Cho was a big beast. But what I have notice that after going 2-8 I finished my stattic shiv and my IE I ended up going legendary after a few minutes 10-8. That's his strength getting that damage from IE plus the crit damage bonus with the crit chance being 90% he is a beast. That is really his time to shine, but I think it is too severe. I ALWAYS end up pushing the lane trying to harrass getting my E stacks up some getting my whirlwind Q it is really bad for me to push up that much, their gragas ganked twice well and I died both times.