I confess, I *love* carnage, so no worries there! ;-)
I was watching for that explanation and how it applied to trellwolves, and I didn't see it. I do think it's a plothole.
I totally agree. It did seem surprising that there weren't any female fighters at all (at least, if there were any, I missed them amidst the metric shit load of minor characters! :-). There didn't seem to be any explicit social prohibition against it...it would be nice if the authors addressed it in a sequel (which they're apparently thinking about, after their other current projects are completed).
I did really like the way that the troll genocide *wasn't* swept under the rug; and I thought that Isolfr's plans for his daughter were interesting both from a gender standpoint (as his reaction to his observations about the female smith) and also from a political standpoint as well. Good stuff. My main complaint with the book was that it was too short!