Yes, I wonder who has finished the game.
So, the squad at start of the gamre must be chosen (if it exists) just to beat the boss.
One must study the boss in a 1st newb' game, then, once destroyed by the boss, cancel the game and restart it with this special squad...
Some may prefer not to play, not to buy.

I beat it first time I tried, with 2 party members surviving the initial salvo of attacks. So yes, one member of my party died before I was allowed to act, and I still beat it.

Tracker/demolition
Scrapper/tinker
Medic/psyker

The Medic died immediately.

What was your squad setup? I am suggesting the devs add some capability to respec ability points, which I think would help you.

I was able to win with a mediocre squad I wouldn't recommend:

Tech / Robot Mastery
Miner / Quartermaster
Bruiser / Quartermaster

The Miner had Corrosive Barrage to strip armor, which all the multi-hit cards could take advantage of.