I used mostly the Fireball spell and ebony sword (or whatever its called)
Also i used lots of healing potions!
One question. How many DPs are in Skyrim??
I found that I have better luck if I don't try to fight them from range. If I take an invisibility potion and get in close, I do some real damage and the dragon priest can't get off shots with the staff he's carrying. With Morokei, you really do find everything you need to beat him as you're going through the ruin. The weapons dropped by other enemies can be the one that does it. You don't want it to be too easy or it won't feel epic though.
Good luck! 


