Riot, let's be real with Vayne
You can nerf her damage. Increase her cooldowns and mana costs. But you won't turn her into a useless piece of trash.
Why? Because of her W and R. These two abilities are literally the only things that are keeping Vayne from becoming Nunu 8.1 level trash. People stop playing her after the nerfs, thinking that she isn't very strong anymore, but she still is. Her W is genuinely impossible to counter except for shields, which not everyone has, and which don't last forever. Seriously? True damage? Her ult isn't really as bad as her W, except that stupid invisibility she gets for a short period of time, which happens often because of her low Q cooldown.
Vayne is basically a more overpowered version of Quinn. She can do anything. She is a ranged assassin. A ranged assassin with true damage and invisibility.
Now do you know why she is constantly a problem?
Nerf her damage or whatever, but I can still easily see a Vayne hard carry a game and start three-shotting everyone after a few items.
She makes tanks useless.
She does an assassin's job better than them.
She can 1v1 anyone.
I don't know why an ADC champion would be given true damage and this insane amount of mobility, but it's happened. Her Q and E are fine. I forgot that her passive even existed.
Let's take a look at other ADC's.
Draven can dish out insane amounts of damage, but is it true damage? No. Is he going invisible every few seconds? No. Kalista is still Kalista. Twitch seems to be the only other ADC than can match up with Vayne, but he requires tons of peel to do it. Yes, Kog'Maw can just stand there and start right-clicking. Oh! But what's this? Vayne has activated her ult and gone invisible and deleted the Kog'Maw into absolutely nothing?
Vayne scales better than most champions in the game, and the fact that she is a ranged champion makes this even worse. Sure, Yasuo can go insane late game as well, but he has to actually get onto his target.
Nerfing Vayne's damage or whatever actually won't do anything. She plays like Quinn.
If you want to keep Vayne's kit, at least lure her somewhere else, like how Quinn isn't really played ADC.
This isn't a rant, I'm trying to let you know Riot, why she has never become utterly useless.
TL;DR True damage, invisibility, max health% damage, insane mobility, these are the reasons why Vayne has never completely become useless. People just assume that she is after she gets nerfed, but she is not.
Sorry for making this so long btw.
EDIT: Also, no, I'm not saying that Vayne should become pure trash, I'm just trying to prove a point.
this is one of the reasons why no matter how much you nerf her damage , nothing will change
it's her kit , everything about her is just too strong , her Q will make her perma kite and dodge mages skillshots
her w brings true damage for no reason , her E is too strong for self peeling and for running , her Ult brings stealth for no reason
she needs a rework , but if they do , she won't be Vayne anymore , that's why nothing is being done against her