So here is some of my conclusion about difficulty level of the quests in 1 player game to 2 players game.
Journey down to Anduin: 1 player and 2 players game diffiuclt level is same. there is no really big difference.
Hunt for Gollum: With 2 player game is more diffucult cose is start to be really boring and you will still win only take more time.
Carrock: Here is another story. In the 1 player game quest is quite easy but in 2 players game is start to be really difficult and much more dangerous.The best example for now how is should be.
Rhosgobel: Difficult to say cose this quest need really specific deck building then other scenarios.
Osgiliath: Really brutal in solo game and much more easy in 2 players game.Actually is strange but is true.
So what do you think fellows???
but seriously i play alot and cant see how anyone can find the game THAT easy, its just not believable