The problem with Yasuo has never been his numbers. It's his ridiculous through the roof utility. I really can't think of a champion that needs a rework more than Yasuo. There's a reason other champions with short CD knock ups and stuns have about an 8 second CD before they can knockup/stun the same champion again. And in addition to significant hard CC power, he has a rapid cast dash that makes landing skill shots ridiculously difficult, a shield has to be broken before you can even try to hit him with a skill, and then a barrier that negates more than half the abilities in the game when the other two defensive utilities aren't enough.
He pretty much has to be on the more nerfed end of the stick because if you give somebody like this a regular amount of skill damage, he'll have power base damage to go along with hyper utility. And the fact that his two item powerspike is pretty much the most powerful two item powerspike in the game doesn't really help keep him under control.
They need to cut back on his utility and then increase his damage.