According to Vandiril's Video, Whoever is in Mordekaiser's ultimate won't get the heal from her AoE when she hits all 4 weakspots, herself included.
This means Fiora literally loses one of the 3 things that make her a good duelist because fuck you.
And while I personally hate fiora and she can rot in a Noxian prison for all I care, this is borderline unfair even for my level of bias against her. Making her Ult heal downright useless anywhere outside of a late into the game teamfight.
You could have made Mordekaiser R unparriable instead of this.