+1 for AoE damage. Feels fresh and fits siege units perfectly. If it proves too powerful, it could replace the double attack promotion, couldn´t it?
As a sidenote, the idea of more damage against full health units is intriguing, would make more sense for both siege and ranged units than damage against wounded, which feels more like a melee line perk. It would be neat if archers and siege units alike would do proportionally less damage the less health the target has, but maybe it is all just too much work for too little gain.