vayne is not a tank buster
i got downvoted to oblivion for saying this. https://www.youtube.com/watch?v=gZDJqpFspmg her design was an assassin/mobility/carry. look at her style, her kit:
-stealth
-bonus ms
-had high burst on her old E (440+1.0 AD)
-tons of bonus AD, and base true damage, her old Q (75% bonus damage) could remove 1/2 of a squishy hp with a critical strike.
if you look at this kit, it's an assassin kit Repertoir said that vayne was released at a time where riot was only thinking to a good experiance on a champion. The %hp damage was a mistake, Riot has to remove the %hp damage (or nerf it) and buff her stealth, E damage, Q damage, and W base damage.