Easy
Freehold
Waycrest Manor
The Motherlode
Temple of Sethraliss

Medium
Mechagon: Junkyard
Kings Rest
Tol Dagor
Underrot

Hard
Atal'Dazar (this is easy if you can handle the poison guy)
Mechagon: inside (forgot name)
Shrine of the Storm

Very Hard
Siege of Boralus