User blog comment:ClariS/Fiora Remake/@comment-109.165.70.66-20121003124308/@comment-4881935-20121004032053

Not having a counter play against her innate passive is not a problem in my eyes. It's an on-hit effect that just there to promote more auto-attacks from Fiora, which means, she wants to stay in melee range more often which allows you to damage her as well.

If there is any form of counter play, its healing and preventing health lost since the damage is dependent on missing health. If the target manages to heal themselves before each exchange, then the passive damage isn't getting stronger. I think that's some form of counter play.