Attacks that cost HP or that do more damage at lower HP may be "high risk, high reward," but the risk and the resource expenditure is shifted from the player to their healer. In a single player game where you control all of your party members, this is fine, because you have control of both sides of this. In an MMO setting, though, it doesn't work as a job theme. You'd end up deliberately throwing yourself into harm's way for more dps while your healer picks up after you.

The one area that you can work on is the lifesteal angle, as per Final Fantasy Tactics.