Suggested nerf for Yasuo
Anytime he uses his weeb sword Katana to hit any champions who have the 'tank' tag. It receives damage, due to being a heavy, fat sword made of crappy iron folded to make it somewhat comparable to western steel, which replaced folded iron in the west. Each hit on an armored tank reduces his total AD by 5%. And it remains that way until he backs and buys a new Katana. As a compensation buff if you stand still long enpugh he will begin oiling his high maintenance sword, making it slightly more resilient to damage.
Also as a side nerf armor pen is nerfed 25% on him since his short, fat Katana lacks an acute point and half swording techniques for finding the weak points of armor. Since it was designed for chopping down unarmored peasants. On a side note Fiora gets a bonus against armored opponents.