Their main advantage is not their damage, defence or HP really, it is (IIRC) the invisible stat relating to mass. It enables them to stampede through essentially anything (not Darknut though, I checked). Fun times! It enables them to stagger large groups of enemies without having to stop, which allows them to take on much larger forces, compensating for their low troop numbers.
I would lower the stats , especially mass, and raise the troop numbers. That should make them a little more fallable.