Even on easier difficulties, I think dragons get stronger as you progress, not just in level but in the story as well.
I will admit, I'm taking some of them out. They have a good amount of HP, a lot more than my usual fare of enemies, but it doesn't do much to me either.
That'll change when I feel confident enough to bump up my difficult a tad (I lowered it a while ago because an Ice Troll kicked my ass).