User blog comment:Tiredman2/Mass Effect Plot Holes and Contradictions/@comment-1679409-20120826182837/@comment-4953843-20120827034450

codex: husks were the discarded flunkies from reaper processing procedures, the ones they deem unsuitable for cuttlefish making. aliens, having more or less little "genetic variance" than humans, make excellent specialized footsoldiers based on their races' innate hats.

everyone else is "not varied" enough they can be shoehorned into specific battlefield functions while humans retain their "versatility": just because we haven't seen scions, abominations, praetorians and other ME2-type husks that ain't distinctively collector in ME3 doesn't mean they aren't deployed somewhere in the galaxy.

and i don't think we've seen/we'll ever see the full display of huskified galactic civilization. you know, gameplay/engine limitations.