The concept of “healing by attacking” needs to incorporate ways to approach healing that require you think about different attack spells to use when healing is required. The problem with Kardia currently is that every DPS spell has a Kardia effect and all Kardia effects are the same. Whether Kardia exists or not makes no difference because you’d be casting the same spells in the same order anyway. Your choices don’t matter.

If you change Kardia’s effects from restoring HP to generating gauge, we get the same dilemma.