Fenixp: Not hard enough for me, and I suck at turn-based games. Also, when you lose a fight, most of your crew is injured, but none them dies - they can only die later on due to injuries if they go untreated. And you get experience for the fight, so you don't just lose everything.
This is why the first thing you should do is go into settings and increase Injury risk. They can become more likely to sustain injuries after battle, quite likely to sustain them if they have fallen, even if you get them back on their feet during battle. Chance of death while they are fallen on the floor during battle, and most importantly probably in this case, injuries will actually lead to death if untreated, rather than fatally injured :)
(not all from one setting, it's several)
You can also increase the AI so they start playing better, like actually using all their abilities. On the best AI you can also forget about them foolishly triggering any attacks of opportunity :)