what they can do is make more common mechanics where something bad happens whenever you take any damage from it; even 1 hp.
i can only think of 2, ifrit's vulcan burst (if it deals ANY damage, people get knocked back) or the dash from e5s (if it deals ANY damage, it gives a damage down)

that way shields become relevant beyond just being extra hp, but the devs said they want to more into pure healing being more relevant than shield healing.