What's Vayne's strong point?

Assuming that people call Vayne the best ADC at the moment, at least for soloQ, and one of the best carries late game, it makes me think what part of her kit is actually so devastating. And then, it hit me. What does she do different than any other ADC in the game? Self protection.

She already has a short dash that can dodge skillshots on a fairly low cooldown. She already has a knockback that can make her push away divers and even stun them. These two abilities are already strong enough to make her safe during a teamfight late game. Add to that the core item PD that protects her even more + possible support from her team, it's already insane defensive power.

But, the biggest thing is her invisibility, that, as of the removal of Pinks patch, cannot be be negated. I believe this is the true breaking point. You start the team fight, and most of the times, you can't to catch out the ADC, based on target prioritization. Apart from possible Q / E safety as mentioned above, let's assume she actually does get locked down and the enemy wants to go hard on her. She can use her Q once the CC on her is over,kite around / away for 1 second, while basically becoming immune to non AoE damage, and then the enemy is forced to focus someone else, so that they don't waste DPS. During that 1 second, Vayne resurfaces in a unknown position, able to DPS for free, assuming the main engage is over and she can now peel and kite away more efficiently.

The fact that during that one second, you don't know where she's gonna go, so you can't really follow her is a problem, and she can use that like 4-5 times during her ultimate. Many champions have repositions, like Lucian, Ezreal, Caitlyn, but you know where they are gonna go and can still go ahead and follow or damage them. Can't do that against Vayne because you can't know where she's going.

I believe the rest of her kit is good. W for tankbusting is fine, Q damage MIGHT be a bit over the top, E is fine, ult numbers are fine. I believe what truly makes her so broken late game is her ability to stay safe based on her kit, items and support.