I've hired no generic recruits. Although I have accidentally entered the recruit menu I immediately canceled out of it.
I have all the yellow stars in the normal game and beaten all the bonus challenges but this achievement refuses to complete. I've also beaten both endings in NG+ (with blue stars on Normal) and the Hero Mode+ achievement also fails to complete. However I do show 88% completion for Hero Mode++ with 159 yellow stars and no generic heroes.
I'm playing on WinXP through Steam. And I just realized, in complete shock, that the the achievements are indeed registered on Steam as unlocked. :shock: Awkward.
Afflicted savegame attached.