To clarify my OP, I intended this to be a skill or trait that all creatures would have. Most ordinary mobs would only have a base skill of 1, meaning they could only damage one figure in a unit at a time. Packs of mobs, such as a pack of wolves, mites, and other grouped creatures would be able to damage more than one unit because each figure in the unit could damage 1. Stronger mobs such as ogres, dragons, golems and the like would naturally have a higher rating in this skill, so they could damage multiple figures in a unit.
By making this a base skill that everything has, it would help balance combat and greatly increase depth. This could also be a trait purchasable for trained units. Of course, like many understood, this would be a skill common for warriors, and perhaps obtainable by defenders, assassins, and governors to varying degrees.
Dont forget that it would scale perfectly alongside the increasing figure count in trained units due to tech, because a champion would be leveling as the game progresses. It could also even be that warriors increase this skill automatically on levelup or every other level.
Along with better balancing of weapons and armor, I believe this would make combat a lot more dynamic and make groups of mobs/units a bit more relevant.