[Valerius]

I've also had good success against them using air mages with bodyguards along the lines shatner describes. Air shield to protect against the archer, lightning bolt to kill the knight and Bogus (even if you don't have many mages the lightning bolts will increase his fatigue which improves your melee troops' chances). Once you get past those two the others aren't hard to kill.

It's a hassle having to devote resources to dealing with them so early on but maybe you'll get some decent magic items out of it.