There is more as to why Vayne is OP

Tank meta - First and foremost, Vayne is the premier tank buster with % total-hp true damage and synergies with crit. being at the top of the food chain simply supplement this.

Assassin nerfs - This also goes without saying, nearly all of Vayne's serious threats got their burst nerfed so Vayne has a chance to attack and fight back. Invisibility with virtually no counter-play - I hope you have on your team, but you better win the game early or it's fucking over anyway.

Counter nerfs- Pretty much all of her counters, with the exception of . With the nerfs to all armor pen ADC builds, which stifled Vayne fairly well due to her extremely poor base armor (19) and barely decent scaling (3.4). are all significantly weaker. And even some of Vayne's other AA reliant ADC counters have been nerfed fairly recently .

Fuck you ADC bruisers, such as and are also weaker, because of the changes to Fervor.

Incredible build synergy - + = Obvious great damage but Warlord's + Bloodthirster + Mecurial's + Red pot = ~30-100% of her max HP return on every single auto in the late game depending on Vayne's missing HP. If you mix this with someone like Janna or Lulu Vayne is basically invincible short of catching her out of position with all of your damage dealers ready to burst her down. (Too bad she can have 2 CC cleanses and takes ~12% less damage due to her tank building Knight's Vow)