After noticing that you can color your reticle (or just show textures around them) based on mob properties, I believe NB's Assassin's Blade would also benefit from a small separate add-on in the same vein.
Just showing an indicator of some sorts around the reticle if the current target is below 25% to use this execute-style ability would probably better than staring at numbers on the health-bar or trying to guess via overhead hp-bar. |