For me it is the Trollshaws. The reason is all the travel from place to place with low quest density and the disconnected quest levels. Start at 30 and jump to 38.
I have to agree, and the enemies don't seem to be scalable with you character, they seem to be capped at around 25...
I understand what you guys are saying, but I must say that I strongly disliked Angmar... It feels depressive and is visually very heavy to do quests in a land such as that one.
