Vayne Scales way to easy on just atatckspeed due to her %hp true damage combine a couple of attackspeed items with auto attack resets and your golden.
Im not a vayne player but what i see all the time is first 2 items attackspeed.

Unholy amounts of magic damage
True damage nukes applied ultra fast with tons of attackspeed and aa resets
Fat AD steroid on ult to make the crits hurt alot
Healing on crits so no lifesteal is needed until later.
Invisibility so you can get your aa tumble condemn into wall before your opponent can do anything about it(don't forget invisibility got buffed)
Lets not forget very strong self peel through condemn and strong kiting with tumble, but then she also has ridiculous chasing potential with passive, you can not get to her and you can not run from her its a bit dumb, sure the kiting requires some skill from vayne but ist still annoying as hell when she can just condemn you away, unless you have 2 gapcloser youre fucked
Its so stupid to deal with you can't build defensively vs heavy crits bursts of magic damage on hit and true damage nukes applied by auto attacks
Vayne has a few weaknesses but they can all be covered by items masteries and support.
Laning is not the best which is where your support comes in to help.
No waveclear/pushing power so you get your shiv first and that is suddenly fixed.
Lack of sustain in first two items, unless you do the old build, but you have the pseudo lifesteal and you have feast/vamp and often your support can help via direct healing or targons healing.