Finally giving in to the Vayne hate!
After witnessing this Vayne 1v3 part of our team TWICE, I'm done. Please, just please, hit her mobility. An ADC is supposed to be strong, but not strong enough to fight all on her own against half an enemy team. Most ADCs need a support or a team to peel for them so they can put out their damage... Vayne has self-peel on a very low cd (2 sec tumble?), invisibility to make it even harder to hit her, and a knockback + stun in case you do get close. I don't even care about her damage at this point, it's her safety/mobility.
Also, if she lands an auto on you, GL. You're dead, because while she's chasing you, she gets a bunch of movement speed on top of her low cd tumble to stick on you.
Don't nerf her true damage, nerf her mobilty...
you're welcome