Shaco has a constant 54%+ win rate in ranked (56-58% in gold/plat) while Yi has a 49% win rate, he needs the nerfs.
Getting tired of people throwing around win rates like it means anything. The list of factors that go into win rate is so obscenely long, that using win rate as a balance metric is silly. Take ezreal for example. He was broken as hell before, and probably had a 40% win rate BEFORE he became popular. Now, he is still getting nerfs after being gutted, and is still one of the best carries. Stop using win rate as a metric for balance, especially as your only metric for balance. And like the poster below you says, the people who have played shaco after he was gutted a long time ago are the people who know how to play him to his potential. That means they have a higher chance of winning because of sheer experience with the character.
Onto the actual topic. AD Yi, even with the reduced channel time, takes a massive kick in the balls from this. So does AP Yi. Once again, riot hits the wrong areas on a champion. Meditate is not reliable, at all. Especially that nearly every viable champion, and new champion, has a way to stop the channel. That renders the skill USELESS. Unless that is fixed, which this change does not do, it will remain useless aside from the hilarious abuse situations where he stands there laughing for the channel, then gets blown up anyways.
As for Shaco, I have no words. Nothing. What is wrong with him? He takes lots of practice to get the hang of. Is he broken to the point where he is over rewarded for mastering him? No. His damage/usefulness peaks, and then drops like a god damn meteor. That makes up for his early game ganks. This nerf, if it goes through, speaks for itself already.