On Vayne (pls read before downvote; i'm not just complaining)
The community as a whole thinks Vayne is unbalanced. The basic problem is that she scales incredibly hard into late game, has a decent early game, and a solid mid game. She is literally strong at every point of the game, which is something nearly every other ADC can't pull off. I do love playing tanks and bruisers, so I should complain about her %health true damage. I have to say, this is NOT her problem. In fact, the true damage is absolutely core to Vayne's identity. The majority of her damage is still physical, and Warden's Mail gives the attack speed slow to itemize against her. Vayne basically needs to have her early base stats (AD, AS, HP, maybe MS) nerfed, but be given higher base stats late game. This would emphasize her late game, and make her more manageable early game. Another thing I would suggest is putting more of Vayne's mobility into her passive (lower her movement speed, but increase the bonus MS from her passive). This would make it easier to actually catch Vayne when she isn't being completely stupid, as many Vayne players are. How many times have I been saved by the enemy Vayne's condemn for crying out loud?
The ADC reworks are coming up, so hopefully those changes will somewhat fix her problems, but it is quite likely Riot balance will eventually do something similar to what I'm saying. Either that or nerf Irelia, like they should :P
and basically every single adc