Even against a non tank, silver bolts alone increases your damage output by almost 80%. Max health true damage is an absolutely toxic mechanic in every way.

Vayne not only has that, but on demand stealth on top of self peeling and medium mobility is pretty fucking good for an adc.

No, just because shes weak pre 6 doesnt mean she is a weak champ. That's like 50% of all the champs in the game right now.

You always have relevent damage no matter what stage of the game, against tanks, your W will deal more damage than the rest of your kit combined.