Opponents levels are fixed in the game, so if you find them too hard, the only thing I can suggest is to go back to an earlier section and gains some more levels (kill monsters, do quests etc) before trying again.
I've heard ED is much harder than DKS, but can't comment as I've only played DKS. Certainly DKS on 'casual' difficulty is very easy.
Otherwise look on the ED section of forums for recommendations on build/equipment/tactics. Good luck!
