Idk if this is somehow intended, but it makes the Staff (safe for the extreme parry bonus) fairly useless for anything but pure casters.
I thought it could be a good tool as precast for when missing a Parry or getting overwhelmed - but the Shield seems to constantly disappear (not timing out) due to incoming damage, even if the damage was parried and not actually taken (aka a full supposedly 200+ HP Shield breaking after one or two <1 Damage Parries).

Considering the opportunity cost of 40% health per cast, vulnerability during cast animation, as well as having to use a Mana food and losing out on significant extra Health or Stamina from other food - using this thing seems more dangerous than not if the Shield just pops despite taking practically no damage and not timing out, and suddenly being left with just 40% HP loss and less Health/Stamina from not using better non Eitr Foods, with nothing to show for it.