Let's talk about vayne.

http://champion.gg/champion/Vayne Even though vayne looks op on the surface, she isn't. I'm just gonna break down these statistics. 51% winrate with a 22% playrate Definitely seems powerful because (most of the time) the higher the playrate the lower the winrate should be. But wait. Her winrate is 45% up until the 33 minute mark when it just breaks 50%. Her winrate then steadily increases and tops at about a 56% winrate at 40+ minutes. Nothing too special for a late game scaling champion. Her playerbase average is 122.92 games played, that's the most out of any ADC according to champion.gg. On top of that players with 125 games max out at about a 53% winrate, that's nothing special. Finally she has some of the lowest damage out of all the ADCs too. (12/17)

Conclusion-She is not OP. Strong, yes, but not OP. Her buffs were arguably misplaced but she still deserved them. With the upcoming assassin update her winrate is only going to decrease over time. She does not need buffs.