I myself completed a difficult map using exactly 3 of these creatures, with a Knight hero defeating a Warlock with 4 green dragons and more than a week's worth of accumulated experience, without losing anything. I'm not even talking about 5 skeletons with a bunch of other undead and dozens of cyclops with +++.
In Heroes of Might and Magic I and II, the damage a hero inflicts on an army, or even a single dragon, can vary by almost an order of magnitude, depending on the defense and attack of the heroes.