In very few quests can you combine four powerful, high-threat heroes and expect to keep your threat under 50. But this week, Escape from Mount Gram is the Quest of the Week, and at the beginning you set your threat to the threat of a single hero you choose to rescue the others. Note that this isn't your starting threat, so starting at 50 threat, which is possible with Gwaihir, would still eliminate you if I'm interpreting the rules correctly. So the highest threat you could start with on this quest is 49, which could be accomplished with Théoden or a few other ways, but I decided Grimbeorn the Old would be great at handling the later combat, so this deck starts at 48.
Círdan the Shipwright or Treebeard make great starting heroes, with access to high willpower, though Aragorn could be a valid choice as well with his innate readying ability. You obviously want to see Strider quickly, though with Círdan the Shipwright or Treebeard it's not entirely necessary. You'll start in secrecy, so this is probably the only quest to consistently play Resourceful with Bond of Friendship.
Is this the best deck for Mount Gram? No, you can definitely make a more consistent deck in more conventional, lower-threat variants, but that's not really the point. Of course, this deck is still capable of smashing Mount Gram, but many decks are. This is all about getting four of the highest threat heroes together to make Sauron quake in his boots without threating out.