I'm not entirely sold on the idea that the upcoming battle will be a one-sided curbstomp. For all that the Imperial army is surrounded and outgunned, I doubt we'll see anyone break and flee. The Rhomans will probably kill them, but if they run from the field, they'll almost certainly run afoul of those damned partisans, the ones who have a habit of eating the people they kill. The fact that it was only one or two partisan bands that turned to cannibalism won't matter; to the Imperials, every partisan will be a man-eater.
In addition to which, as much as the leaders of the Imperial army hate each other, they're all in the same trap; the only way they can get out of it and go back to killing each other is to stand together and either beat the Rhomans or at least fight their way clear. And as battered as the Imperial army is, it still has teeth, and there's nothing more dangerous than a wounded and cornered animal. Casimir especially knows that his survival depends on fighting the Rhomans to a standstill long enough to retreat, and I imagine that 'Bone Breaker' can also expect a quick death at best from the Rhomans. Vauban may be less desperate, he's just a professional following his king's orders, but Theodore will almost certainly prefer to fight to the death than admit the possibility of capture; his pride won't stand for anything less.
I concede that the Rhomans will probably win, but it'll probably be a Malplaquet rather than a Blenheim.