I come up with idea about what could be changed to make yasuoo less opresive in lane.
I though about his passive shield and how weird it is. On one hand it is free shield with pretty strong value, on the other hand you try to aa him in lane just to pop it, wait moment to fall it off and then eventually attack. Other defensive is his e, that allow to jump like crazy. Its great spell, but a lot of people (the weaker ones) just spam it w/o any concrete idea and still manage to avoid a lot of spells.
So what you think of removing his shield AND his e 10s CD. Instead now his e would cost 33 or 25 flow (numbers to change). Flow would generate as it is now. In compensation Riot could also reduce W cd. So if your bar is full, you could cast it 3-4 times in row on one target (removing difference between fighting in minions vs solo) but spaming it mindlessly would be worse. And there wouldn't be that weird ,,try to aa to remove his shield, then cast spells" scenario. Casting it on same target would just reduce its dmg as it works with urgot legs etc to prevent lvl1 burst.
Tl:dr: no passive shield, e cost flow but dont have cd on target.