Giants and trolls are really OP but giants are usually in the plains (though unlike the demos, they will attack you even unprovoked) and don't regen health and are rather slow in attack and in movement, but those snow trolls, god damn it, even though I had decent destruction magic (though I'm a 1h with restoration in the other hand) and fire did squat, wasted all my mana but I barely scratched it. After several deaths my tactic was "run and hide" (even though I was afraid for my follower which wouldn't be coward, but while he was brought to his knees I ran away and later he caught up with me...don't know what happened, don't really want to)
Btw I only got 1 dragon shout plus the one I got at the top of the 7000 steps mountain, I must be crazy cause it does basically nothing, it kind of stumble an enemy but I seriously hope there are better ones out there.
Also, while dragons aren't that though so far, if you're not proficient in either destruction bolts or archery, you basically have to wait till you find that one spot where you can get the dragon to actually land before you can attack it. Again thank god for companions which are better at archery than me.