I don't like the idea because it removes player agency, the same way that tank LB3 can also cheese a mechanic. I like having the ability to choose whenever I want to nullify a specific mechanic, and having to choose which. It brings tactical agency, and this game has already removed way too much of the battle system choices and player agency to my tastes, and I don't even play tank.

Which brings me to my point though: make all invulns a one per fight card only. You can keep the different recast timers in dungeons and multifight scenari to account for Hallowed being technically superior to anything else so it has a higher recast, but each tank should be allowed only one invuln per fight, and that's it.