Ha. Umber did the same, sadly they were all peons. But they did burn 3 outposts before I got them... actually, its not a bad idea, send some dispensables to do that. Of course, ideally you send a single dispensable on horseback with scout stuff so he moves really quick ( 6 moves) and nuke everything in sight, but hey, im not complaining.
Resoln did the same thing with a massive army btw. Which I then nuked with Pillar of Flame three times, and then shot with my Archers. I went for their Empire, tossing Fireballs, and wiped them out. Oh, and heroes dont hop between spots in fights anymore. They kill my archers now. Bad heroes! BAD!
(AI level set to challenging as well)