it's fine on garen since his % health true damage is an execute.
It's almost fine on Vayne because it doesn't become too extreme.
But fiora, oh does it NOT work on fiora. It's bad enough when max health damage increases with AD, but when % max health TRUE DAMAGE, a damage form with LITERALLY NO COUNTERPLAY - that's FAR past the line, WAAAAAY far past the line.
Fiora has been an extremely toxic champion ever since the rework (and was even more toxic pre-rework, but at least she wasn't viable back then, technically meaning the new fiora is worse). At least make her damage counterable.