Skill synergies.

I was thinking about linking the pack hunting ability with the Orcish Blood Fury – pack hunting allows all units to attack in a group, and Blood Fury makes it so that it doesn't seem overpowered.

I only see this working for Goblins, as they are cowardly, and their attack stats aren't very high, so it would suit them, but there are too many combinations for melee units, while there's not much room for ranged units.