@ Reverend Zombie,
as I said, I'm trying the potential of Horrors in my actual SP game using Mictlan.
Maybe it isn't a very worthy example but trying to soften a Marverni army of about 80 mixed units + a "quite well organized" PD sending a lesser horror to the enemy province before my actual army of blessed Jaguar Warriors (they wouldn't have needed that help anyway), with my surprise the lesser horror was able to kill some of them and to rout everybody - so my army had only to fight the few units that were arriving for their reinforcement.
It isn't a great example, Marverni's PD is IMHO quite poor and their army did not have good mages, but as you asked which PD a lesser Horror was able to defeat, well this is one. ^_^