It might be a bug with the new Infinity Edge and Brawler's Glove, since IE is now doubling your crit chance, or it could be a bug with the new IE interacting with Yasuo's passive. I'll jump into a practice mode game for a bit, help you find out exactly what the problem is and then you can submit a support ticket to Riot explaining in detail what the issue was just as I do. Well, I would, but the game won't launch for me at the moment. You could research this bug. Pick Yasuo and test buying IE and glove, see how much crit you have, then play any other champion, buy IE and glove, and see how much crit you have (remembering that it should be 20% on them, not 40%). And if you get 10% on the other champion, you know it's a bug with IE. If you get 20%, you know it's a bug with Yasuo passive.