Sideways to Victory!
These decks form an amazing team! You will aggressively turtle your first turns, blasting through side quest after side quest as you build your forces so that the main quest becomes a piece of cake (or at least manageable on the more difficult scenarios).
Hirgon's Army should be able to handle all of the combat. There are a lot of sentinel defenders and ranged attackers in case enemies get through to the questing deck, but more often than not, you should be able to engage all of the enemies. The Vigilant Dunedain does great work in this deck because you will get a side quest explored on the first turn, and the Raiment of War and Honor Guard (and Keep Watch) give him some staying power. Legolas is good to look for in your opening hand so that you can draw cards. Otherwise, use the side quests and your low threat to build up an unstoppable army of tactics allies.
Sideways to Victory is a powerful questing deck despite not having many allies. Rossiel and Thurindir should quest for at least four most of the game, and Arwen, Firyal, and Ghan-buri-Ghan can add some punch to that too. Drawing into more side quests shouldn't be a problem. There are plenty in the deck, The Road Goes Ever On will help you go looking for them too. You should use your first The Road Goes Ever On to fetch Keep Watch from the tactics deck. Arwen is mostly there for the card draw. Look for an Elven-Light in your opening hand, which will mean at least one extra card all game. Protector of Lorien makes it even better, and you can spend just about all of Arwen's resources on card draw. You need to be judicious with your Lore resources, responding to what the encounter deck is doing and being patient. You might go a turn or two without playing anything because you're waiting for the right moment to cancel a treachery or the right location to add to the victory display. You should be able to quest like crazy and really lock down the encounter deck when things get hairy.
These decks are fun and work great together, while providing a different approach to playing LOTR. Have fun!