Army ants are an ant species which gets its name from traveling in vast hordes. They protect the reproducing queen of their colony and devour anything that gets in their way. Suddenly, there is a precedent for orcs in nature. If we go further with the ant similarities, one could have reproducing orc mothers produce pheromones which prevent orcs from reaching sexual maturity, thus leading to orcs of sexless appearance. The orc "queen" (I'd probably refer to her as a War Mother), is supported/protected by a group of guards/husbands, the orc equivalent of drones in bee hives. Of course, the War Mother should be no slacker in combat either. In the real world, naked mole rats are a species of eusocial mammals, so its not as unlikely as one thinks for a species of pig-like humanoids having an ant-like reproductive cycle and social structure.
Suddenly orcs seem a lot more interesting don't you think?