This, plus the linked articles seems to cover it all - excepting possibly the differing ratios of wounded to killed coming from how quickly (or not) the wounded get to aid stations and then are evacuated - and the relative level of first aid immediately available.

I would expect these relative levels to forward feedback to some degree. For example, if you know getting hit means you're likely to be left to die, how likely are you to try to retrieve one of your buddies who is down? Contra wise, if you know for sure one of your buds will get you and that will lead to rapid evacuation, how likely are you to go get your bud? I would guess that on the negative side of that, not only do you have fewer recovered wounded returning to the front (or less taxing duties), but less effective soldiers overall.

Just thinking it through. As I've mentioned before, no armchair to pretend to be general from. :-)