Yasuo has Gangplank Syndrome
Everyone who has played in Season 2 knew about the terror that was the Gangplank top cheese. By running 1 crit chance rune, and the mastery that gave 4% crit chance, Gangplank has 5% crit chance at level 1. If he prays to RNGesus, he crits and wins lane.
What happened after this? Gangplank was nerfed. Heavily. A unlucky crit meant that you would be losing lane just as you got there.
So Gangplank was heavily nerfed for this cheese style. So why is Yasuo similar? He gets double crit chance making it exactly like the level 1 Gangplank. Its easy to cheese your opponent with early level crits with no penalty. At least GP is gated by resources to keep a lid on his ranged poke. But Yasuo gets to use his at no cost. Crits in the first few levels are very strong, Ashe gets 1, Tryndamere might be lucky to get a few provided he can stick to his opponent.
So can we increase the early Crit damage reduction on Yasuo to bring his early game damage down to highlight the emphasis on his late game strength? Because the power spike that he gains with Shiv+IE, is incredibly high and makes him very snowbally in the mid game.
Something like -30/-20/-10 at 6/11/16