I find wins/losses right now are more heavily driven by assassin mids. Namely...... Zed. If he can't get fed mid, he can always just use shadows to cross map quickly, and kill someone else. And once the player learns his kit, it's not hard at all, and has very little counterplay, since he's more mobile than almost any other assassin, and has more damage packed into one skill than any other assassin. His Energy pacing also perfectly matches a roam playstyle, because every time he reaches a lane, he'll be 200 Energy and ready to ult/etc.
Every time I mid vs one, he can't kill me, so he just avoids me. Roams bot/top, but my bot/tops don't listen to pings 30-40 sec ahead of time. They freely feed, and then all I can do is use turrets to occasionally kill him once we cross paths again.
Bots can carry, but all it takes is a solid CC to kill most of them. Mid Assassins......particularly a Zed, cannot as easily.