So vayne has +70 AD, and +70% AD
can also crit on top of all those steroids for reasons.
why? "because she is an assassin secondary".
so you have someone that can fullfie the niche of an actual carry like kog'maw, while also able to fullfie the niche of an assassin doing a non-delayed assassin lvl of burst damage+mobility/stealth, while also having hard cc and use the mobility/stealth to survive against bruisers.
hm, why? is it because she is low ranged? because that's bullshit, low range doesn't mean shit if you can get to your target with mobility and oneshot your target without her to doing anything.

to peel herself from every kind of melee fighter, carry or tank. I don't think against a good Vayne, in a regular Poppy would stand a chance to land any of her abilities without some level of poor positioning simply because of those self peeling tools.