Actually, The People repulsed them and they picked up a giant pile of other nomad's people to use as fodder. That 2/3s of the force killed was the fodder from other tribes. The Hero units were not even in the army that got squished.Martial 13 is a lot. Even with two crits we still ate away at a massive portion of the nomads. With Iron Weapons we're in a better position than we were at the start of this turn and our people are out for blood.
So its a matter of versing 2 hero units in their favored field (military) in their home terrain (step) with a nonhero unit. Unless the rolls go utterly crushingly in the favor of The People they aren't going to obliterate them. What is at risk on a fail is not just the military... it losing psuedo-star metal weapons to a pair of hero legends as icing to their victory cake.
A loss here means nomads will keep coming for the magic weapons they can loot with luck. They'll never want t leave The People alone.