So I finally got up the nerve to fight the boss of the Burning Lands wildlands, entered combat and... he wasn't there. There were many, many stacks of fire elementals and fire worms, and no boss. I killed them all and the after battle report said I killed the boss too and I got the reward. I'm guessing he had too many units attached to him and the game only let some of them in, before I fought him I checked and there were two full pages of units, 18 of them, which I'm guessing is too many.