I did some reading after Nocturnal’s post, and it turns out my mistake was doing the introductory mission as soon as it became available. The alien bosses are OP, but it’s meant as a challenge to late game squads, not my team of lil babies.
I wish it had been more clearly gated or indicated that it was not intended as early content, but… well, this game is not really about hand-holding.
Shen’s last gift was challenging but rewarding early on. Doing the alien hunter mission around the same time was a huge mistake but otherwise I’m enjoying the DLC in the limited time I’ve been able to play.