A great deal has been said on the issue of difficulty, here is just an idea which I think could help the issue further.
The see-saw of difficulty seems a very difficult one to balance. There are so many variables: a player's card pool, 'skill', preferring theme etc. it seems FFG are either receiving criticism for the game being too hard (Ithilien) or too easy (the last three adventures).
The recently proposed difficulty levels are a fantastic idea, and no doubt will go a long way to making the game accessible for multiple levels, but here is another idea: What if victory in a quest wasn't black or white. What if there were degrees of success. A kind of victory rating. There is already a universal score system in place, which people use to varying degrees, but imagine if it was specific to each quest.
On the back of the quest card could list three categories of success. Something like 3)Adventurer, 2)Warrior and 1)Hero (Terrible, of course, but you get the idea.) Did you kill the Nazgul? Did the objective ally survive? Did you find the treasure? How many villagers did you save? Etc. Your level of success would be determined by what you achieved in the quest. That way you could well achieve a simple victory in 2-3 tries, but the victory wouldn't necessarily be final. You would have to hone your deck, retry, search every corridor of the quest to get that final, perfect rating. Casual players may be content to achieve a simple victory, where as a more serious gamer might get great satisfaction out of achieving the highest rank in each quest. Video games have utilised this method for a long time to increase replay ability, and seeing as LOTR is a co-operative game, I think it could greatly enhance it. It would certainly cut down on the disappointment many people express when they receive a new quest and beat it too quickly.
Just a thought. Probably not possible to apply to existing quests, but it could be introduced to future cycles. What do people think?