Spoiler (click to reveal)
...enemies that Stage 3 requires you to beat.
Today, I beat it by taking my time and dealing with the immediate problems in Stage 1. In round one, two Umbar Raiders in the staging area meant I could not afford to travel to the Helm of the Stormcaller. Instead, I dealt with the Raiders as best I could. Round two, something else came up that needed my immediate attention (a location, I believe). So on and so forth, and I couldn't attend to the Helm until about round five, when I had the staging area was under control.
That meant the two corsair bosses had four tokens each, which worried me. However, I shouldn't have worried. Each boss can be de-tokened to some degree on the turn you engage them. Drop a small attack on the lady boss, and she'll lose two tokens total. Drop a big attack on the male boss, and he'll lose all his tokens. That's what I did. At the end of the round, they were the only corsairs in play, and they had a total of two tokens.
Between that, and the three Ethir Swordsmen I had in play on one of my decks, exploring the Helm and completing Stage 1 was a snap. This meant no more corsair enemies, and the bosses flipped to being allies. That is the key.
Further, the allies and gear I had accumulated on both decks over those four rounds made dealing with the tentacles pretty straightforward.
Just make sure you give the corsair bosses resource tokens every round. Travel to the location that gives them tokens right away, if you can. If you can handle it, you can travel to the location that makes you go through the deck and discards for an enemy. That will help you finish the game faster.