Hi, I just recently played a game where a Vayne bought static shiv and deaths dance. Every time her static shiv procced, she healed for over half her health in one auto. I think this needs to be addressed, as static shiv deals magic damage, and deaths dance says that it only heals for physical damage. This must be a bug, her healing for 1500 health every few autos was not fun to play against at all and felt very cheap.
As you read, understand I have no concern in this comment with balance. As for your information, it's possible you exaggerated and understated things. Be sure to be clear and more detailed.
Vayne has a keystone called Warlord's Bloodlust that receive health based on AD+Crit. With just 
(gives lots of AD+sustain) and 
(critcal strike), it's possible to regain a large amount of health relative to her maximum health and time of game.
Throughout the game, high-ad item, lifesteal, and critical strike + critical damage-increased items are bought, contributing to every energized attack.
