In the whole battle, I only took 2 skill without Mitsuko’s reflect activated which means my heroes should only lost 120 max HP. But as you can see from the picture below, they took around 30% or 400-500 HP.
Despite reflecting the damage and ailment (see the reduced heal ailment icon), it do not block the max HP cut. I understand that max HP cut is not status effect thus it cannot be reflected. However, Mitsuko skill should have block it as it is a negative effect.
The skill in Mitsuko’s card said that it block other negative effects.
I can confirm that Ursena does block direct mana reduction from Guin (and presumably Leo, Neith, Chao, Li Xiu, etc.)
I thought I saw somebody confirm that Mits did block Ymir’s max health reduction. (I fought him without her and don’t care to slog thru that again with a different team. Hmmm…maybe I will use her when I get to it on hard…)