In the Corsair deck, the strongest card is not
Castamir of Umbar. It's
Corsair Marauder, because that's the card that takes things away. It makes playing possessions extremely difficult. There's a reason the strongest beatdown deck AND the strongest swarm deck in Movie Block play Marauder.
Elves have a choice without
Lady Redeemed - archery! Intentionally, Corsairs were built with no wound prevention. But the Marauder strips all the Elven Bows. The same thing applies to other decks. The best decks against Corsairs run few to no possessions: Knights, Gandalf/Gondor, big Elven events. My tourney version of Knights runs just 3
Gondor Bow, and might run even less and more
Men of Numenor just because of the Marauder. It defines the format.
Galadriel, Lady Redeemed causes similar problems: she makes a lot of Shadow sides not viable.
LR is the best deck and defines the format. It makes it very difficult to play any deck that uses Shadow conditions or possessions. There are still ways to oppose it, like Southron archery which plays at most
Rallying Call in the condition area. Low-cost Isengard Orc swarm isn't a good deck, but it attacks one of the other weaknesses, slow expensive companion setup.
Because she shuts down too many sides, I believe Galadriel needs a ban or errata.
Imrahil's suggestion isn't enough, because the Best Deck (big Elf event) remains the best deck. If anything, it makes it worse, because it means one should play big Elves or Last Alliance. Tbiesty's errata would do it, I guess. Have you tested removing all the starting fellowship cost and requiring just one exertion? That would be my first guess at "balance".