Patience and thinking outside the box. It's not 'cowardly' to duck in cover if it saves your life.
And when you get to higher levels, they do get easier. My tactic for...forget his name, Shattered Point Word Wall and a user of a nasty fireball spell. He took some doing, but repeatedly staving his face in with a shield and wailing on him with a sword eventually brought him down. Shouts help too.
I believe that's Krosis. He was fairly tough, just a shame his mask is useless for my character.
I finished The Forbidden Legend, and got the +30 amulet. Yeah it does help somewhat, but it's definitely not a table turner IMO. The fight with the archer and his fake mirror images was too hard for me; had to tgm (I tried for 2 days, I decided "screw this") and the last fight with all 3 of them was just too much for me but this time I didn't tgm and instead just lowered the difficulty. I really wanted to legitimately finish it but dying so many times is boring.
To make up for my "cheating", I don't use the amulet a lot. In fact, I think I should get rid of it, because "I didn't deserve it"?
I am a level 25 Nord, sword and shield, potions for healing. I don't have much magic skills (not significant enough to do much damage).
I'm surprised by that, I did that quest at around that level, maybe a touch lower, with my 2H Nord. I also had high Smithing and Enchanting at that stage - higher than my Heavy Armour and 2H weapons skills, although still nowhere near 100 - so I was comparatively weaker in combat skills at the time...
What gear are you using? Because I think I still had a Dwarven battleaxe at the time, far below my current Ebony one. Even if you're not perking Smithing, you should definitely use a workbench to improve your armour as much as you can.
Beyond that, DEFINITELY get the Lord birth stone - from memory it's at the peak of a small mountain directly east of Morthal and directly South-west of Dawnstar. It really is a brilliant sign. Once you've got that, head straight to http://images3.wikia.nocookie.net/__cb20111113103513/elderscrolls/images/thumb/4/4d/Otar.jpg/587px-Otar.jpg and make Otar your first priest. Once you've got his mask on, any dragon priest or dragon should become a whole lot easier.
Beyond that, I don't really know what to suggest, you shouldn't be finding them excruciatingly difficult unless you're on Master difficulty... don't get me wrong they're the toughest enemies I've faced yet, but they're still not that difficult unless your character is a bit weak.