The best way to make vayne a fair pick
make it so that she actually has low range compared to every other adc. her role is as the premier tankbuster right? tanks don't have so much range in their kit generally, except for skillshots, and vayne already has the capacity to peel off any tank even if caught so long as she is in a 1v1 situation, so why don't we nerf vayne's capacity to equally trade against other laners on the bottom lane in exchange for her ridiculous tank destroying prowess. you could even use this as just a bandaid, incase you think that vayne would need more than this to be balanced.