Vayne should be labeled an assassin first and marksman second .
If all she has to do from level one to kill anyone she wants is tumble and auto attack one time then there's no reason for her to be considered a marksman. She's a ranged assassin now, period.
And with a 33% pick rate and a 55% win rate let's stop with this notion that Vayne is a champion that takes skill. The only skill she takes is being a big enough game ruining pussy to pick her.