This might help.

http://www.youtube.com/watch?v=Dy48d5gr3C4

A video full of tips on how to beat this mission. Played on Nightmare skill, no less. It might be a bit harder if you started a fresh level 35 character and have no dragon armor, but that should just mean you need to drink a few potions and worry about the flyers a bit more. Best watched in fullscreen 720p.