I took this deck to defeat The Battle Of Carn Dum and The Dread Realm. It has a Narya companion deck.
Briefly: This is a big-ally spam deck that relies on various shenanigans to set up a productive A Very Good Tale. You have the costly allies that can enter play at very little cost (Ranger of Cardolan, Elfhelm), and the events to put them in play : Reinforcements, Sneak Attack. The sweet spot for A Very Good Tale in this deck is 9 resources worth of allies (1 big Harad ally + 1 4-cost ally). You shouldn't have too much trouble recycling your events thanks to Tome of Atanatar. Gandalf is mainly used to draw cards, and can be played gambling style (e.g., play Reinforcements, then draw and play A Very Good Tale).
The heroes : Because of the focus on big allies, Faramir works wonders. Captain's Wisdom allows him to pay and ready Treebeard turn 1. Halbarad is excellent at drawing enemies away from other players and enables Ranger of Cardolan. Théodred generates resources and enables Elfhelm.
The allies : There's a lot of ally readying. Whether it's Faramir, Gimli, Knight of Dale, Treebeard, or Narya from the companion deck, you'll get a lot of mileage out of them. Also many allies have a good enter play effect or are good at sneaking in. Elrond is the healer, Beorn is the boss killer, etc. Son of Arnor can be used in various ways. For example he can enter play with Beorn using Reinforcements to engage a big enemy during the combat phase and kill it without defending an attack.
Soloability : This deck can be successful solo, but only on the strength of the Harad allies. Outside Jubayr and Firyal, it lacks any form of cancellation. For solo, I would replace Halbarad with Balin.