For a champion that is supposed to be about late game, with significant early weaknesses, she has an above average winrate throughout the entirety of the game. Additionally, less than 2% of Vayne players have more than 50 games on her.
Bottom line, she is played by mostly novices on here, and they are still finding a large amount of success on a champion that is supposed to be difficult to play. Her on-hit build is additionally pure aids to play against as there's no way to build against it.
Thornmail doesn't really matter to her. She does a large amount of physical, magic, and true damage. Truly, there's no really effective way to itemize against her, but she's equally lethal to squishies as to tanks.
Plus, (as I've written about before), CDR is too damn common. Vayne's ult and Q cdr interaction is causing her unhealthy interactions.
This is because that shit is on such a low cooldown that she is never vulnerable to being all-inned. She can't even be dogpiled because the stealth duration interrupts point and click abilities like Akali's shroud used to.
Vayne is pretty busted this patch, but honestly it's not just Vayne. Her on-hit build working and her rise of success is due to other factors. But you can reduce her innate reliability in poor hands by making her stealth work like Akali's. That would be a giant quality of life improvement for people playing against Vayne.
Right now she has the best of both worlds. With such high attack speed and mixed damage she can pop out of stealth for a second and still get her true bolts off in one 'rotation' - ie, using Q for stealth duration, aaing, and going back into stealth. It is just as unhealthy as Akali became.
Either revert the ult Q cdr you added (Vayne should be fine to go back to traditional builds now that IE is fixed) or allow abilities to hit her in her stealth, going stealth should not interrupt point and click abilities, the entire damn point of them is their reliability.
