In a game I finished recently, the final battle was (suitingly) a clash between my pretender and the enemy. I was playing as a Bog Mummy and the enemy was a Blue Dragon.
My Bog Mummy ended up alone on the field. Everybody else on my side had either fled or fallen. He marched up to the Dragon and cast Leeching Touch on him. The Dragon lost something like 96 HP, I believe, and my Bog Mummy was suddenly at full health and 0 fatigue. The Dragon whomped on him pretty good in return, but another casting of Leeching Touch patched up ol' Dry & Crunchy, plus it brought the Dragon down to single digit HP. This was repeated once more, and then there was only one pretender on the field. My Bog Mummy did some little something that took out the remaining enemy troops (can't remember what he cast, but it worked well!) and that was that.
(On a side note, it should be kept in mind that my mummy had a power of 10+ in Blood Magic at that point; Leeching Touch isn't always that powerful, but I'm sure y'all knew that.
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Soooooo . . . I think the moral here is that Dragons will eat combat types for breakfast but powerful mages armed with the right spells can still go toe-to-toe with them. If the Dragons haven't transformed yet, then they are often powerful spell-casters in their own way (along one path only, usually) and that can certainly change things, but that Blue Dragon was not a challenge for my Bog Mummy.
Also, before they clashed directly, he ate down my best troops like they were popcorn and those he couldn't reach routed in droves.
This post should not be seen as contradictory to my earlier pro-Dragon one!!