The Siege of Cair Andros progression - tactics/lore
The Siege of Cair Andros is my favorite quest so far and I managed to beat with my two favorite spheres! I have beaten it twice out of a few tries. The first time, I was able to use early Ranger Traps to avoid enemies and cleared the 3 locations and battle quested through stage 5. The second time, The Power of Mordor stole The Citadel, but I was still able to siege quest through quest stages 4 and 5. So I think this pair of decks is fairly reliable.
The tactics deck is not too different from what you would use for a solo deck. It has lots of good siege questers and relies on Gimli to clean up enemies. Chump blockers and feint are good for avoiding those dreaded shadow card combos.
The Lore deck is more interesting. Because this quest is so combat heavy, I have included Bilbo, the strongest combat hero in the game (j/k). Bilbo quests for 2 (siege), helps the tactics deck draw cheap cards, and helps the Lore deck dig for everything Elrond needs (Vilya, Light of Valinor, Imladris Stargazer, etc.) Lore helps avoid taking attacks from enemies with Ranger Traps, Gildor's Council, and Forest Snare. It's hard to kill off any enemies on its side of the table (unless you use Gandalf), but it can chump block to delay while you blast through the quest as fast as possible. It provides a decent amount of defense for siege questing (8 from heroes + possibly extra from cheap allies).
Overall, the strategy is to quest quickly, avoid enemy attacks as much as possible, and kill enemies when you can. There will probably be some sticking around as you sprint to the finish! Feel free to try these decks, tweak them, and enjoy this awesome, brutal quest!