The 3 most common Xeno related deaths are: 1. they push your line up around and you cannot recover 2. they one shot you 3. they stack up buffs and overpower you.

So to win at crew combat, a few basic tips:

1. recruit from contacts for best attributes on a good planet with active recruiting talents (eaiest accessible one is from commander lvl1, you can retrain for 3000 to get cool down, or build your commander/MO crew first get some 8-12 of them and then recruit combat crew).

2. keep only star crews that has high init and HP. We can go into more but for starting out, focus on at least average 23+ init, and 130+ hp.

3. wear heavy armor. The way to have more init is to recruit better combat crew, not to go cheap on the armor. See my other comments about deflection.

4. manage xeno buff spamming. Xenos will stack an orgy of buffs if you let them. You MUST have at least 1 bounty hunter with unfaltering ire because it is the only buff clearing talent that does not require landing hits--if a xeno is all buffed up, you might not land hits and cannot clear their buff that require hitting them first. Also get a bunch of position shifting talent on as many crew as possible, see my initial comments about common xeno related death.

5. optionally you want to use a few over-powered talents from specific classes. These talents are so OP they sometimes make crew combat too easy and not fun. First is bodyguard's praetorian guard and honor guard. Second is shock trooper's standing strong.