Thanks for the kind words. My take on a Space Marine is
in the final Sister Ginevra story, and he's ironically more human than some of the Sisters....
But that said I agree that, compared to men writing about men at war, men writing about female combatants are probably more likely to be interested in character and especially the tension between vulnerability and strength, rather than pure plot and action. I put this very cautiously because I'm going off impressions rather than statistics (and coding data for such a survey would be a nightmare of subjectivity), but I do know what's going on in my head: that women have more "permission" to be vulnerable than men, just as men have traditionally had the monopoly on physical power, though both these things are (fortunately) changing.
Also, minor background/headcanon notes:
- Sister Torres is a Battle Sister from an Order Militant, but seconded to an Order Famulous to do combat training. There's background material (somewhere) that says the Famulous train all Novices, whatever branch of the Adepta Sororitas they're headed for, but I'd imagine they subcontract out the shooting part of that training to the Sisters of Battle proper.
- The novices aren't wearing power armor; there's actually fluff stating you get that on initiation as a full Battle Sister at 18. So I homebrewed a Novice unit that had carapace and justified teenage girls with boltguns by saying they had some kind of Vasquez-from-Aliens exoskeletal enhancement on one arm.