Not a QQ Fiora thread, but...
Would it possibly fit her theme better of finding her enemy's vital weaknesses by changing her true damage to be Missing % health True damage? I mean, she finds a weakness in her enemy and strikes it. Wouldn't it be better thematically if she capitalized on their increasing weakness of their low health?
Not a balancing wizard, but if this went through, I would honestly lower her base damages, and increase her scalings so she becomes a better squishy killer.