I know there are too many posts about Yasuo, but here are my proposals

Since patch 4.18 Yasuo's laning phase nerfed really hard. His base health is the lowest for melee assassin in the game (462 @ lvl1). Besides that his base movement speed reduced from 350 to 340 making his Flow generation from his passive slower.

Two ways to make his laning phase a bit less harmful:

Revert his base movement speed, bring back the Wind Wall (W) passive which gave him a percentage of his flow and make the Last Breath's (R) armor penetration scaling, similar to Zed's ultimate: 20% @lvl 1, 35% @lvl2 , 50% @lvl3.

Revert his base health nerf, bring back the Wind Wall (W) passive and make the Last Breath's (R) armor penetration scaling: 20% @lvl 1, 35% @lvl2 , 50% @lvl3.

Either way Yasuo will be able to survive laning phase if he plays safe and be a late game threat.

Edit: Formatting