An actual balanced nerf idea for Vayne.
Make it so Condemn (her E knockback into walls ability) roots instead of stuns. If she is still powerful then remove the Silver Bolt proc on it.
The last part takes away her Auto, Roll, Fade Away true damage, allowing players to retaliate, making a Vanye think twice about just walking up and shooting them in the face some more. The thought process is, "If you're impaled into a wall, you're not going anywhere." Yeah you're right, you're not going anywhere but that doesn't mean you can't fight back. When has Van Helsing ever impaled a vampire and that was it? Those things will spit, claw and even just rip out the bolt to get back into the fight. So even the thematic vision of the ability is a little...off.
The first part is something that there is very little reason for an ADC to have. Easy access hard CC. The problem with Condemn is, no matter what, if Vayne is being agressed upon, condemn instantly puts her in a better spot. It just isn't right for an ADC like her to be given easily accessible hard CC. Maybe when she was first released it was a a harder ability to manage but since then far more difficult champions have come to the scene. She can Either stun you or knock you back. It's an auto target spell so it's going to happen sooner or later.
Let's put it into perspective. Let's look at the ADC's with easily accessible Hard CC.
Very low mobility, short duration knockback for assisting in managing his axes or other general CC reliant task. Has very limited speed boost. Which isn't used for escaping or engaging but management of axes.
Known as the ADCC. Her ultimate is a rather instant stun but an ultimate. Rather large cooldown for a stun, granted it's global but it also can't be a level 1 ability. Unlike Draven Ashe has no one to get into a fight so her ult is as much of a way to start a fight as it is to keep fighting.
A champion primarily hated because she has so much, safety and damage wit high mobility and a massive knockback. Sort of like...vayne. But unlike Vayne, Trist has no CC pre 6 and her ults cooldown is much longer then Vayne's condemn.
Has a knockback that throws her into the the enemy team. With her ultimate she has pretty good mobility, but her hard CC puts her in more danger than ever other ADC in the game. It can be easily countered but it has a pretty great reward.
So all of these ADC's have the same issue. Their hard CC either has a large cooldown, is used for their lack of mobility and/or they can't use it early on.
Vayne has mobility, Hard CC and large amounts of damage. Wall or not her Condemn is helping her universally. Ashe can miss her ult, Draven can't go anywhere and Quinn can be easily countered when her hard CC is used. The only one who is safe is Tristana who, like I said is hated for her safety, but her CC isn't. She's very illusive for an ADC and giving her easily accessible hard CC is just something Riot should give her that also applies true damage.
I hope this thread was atleast slightly convincing because, I believe nerfing Vayne's attack speed or true damage isn't the solution it's just her ability to shot you without you being able to do anything that is a problem.
A few people might say that I'm just a Vayne main trying to protect my cheese, but I'm not. You can see in my profile that I don't even own her. the only time I've ever played her was when I first saw her on free week and to try and get a better understanding of her so I can fight her better. As someone who is always fighting a Vanye, this is the adjustment I think she needs to still be a pick but not over powered.