I usually withdraw as well for above reasons. Am I right in saying that if all your troops rout at the same time it ends the battle, giving you get the auto calc of losses? I hate it when this happens because in my experience, your losses are much worse than if you withdraw your troops.

I've had it happen where I had 3 HA units near the edge of the map looking like they could withdraw without loss, only for one to rout and in turn spook the other 2 who also rout causing massive losses. It was damn annoying.