I would put demons in second place. They can gate to enemy archers and, most importantly, steal mana. Although, against elves, this tactic is much less effective, especially if the elf hero has a pre-battle shot – for some reason, they love to target imps with it. But aside from this exception, it's a very useful ability.
And skeleton archers are good – you can raise a lot of them. You defeat a bunch of gremlins or dryads, raise skeleton archers – great!
В "Героях" я где-то посередине между дилетантом и любителем.