Profligate dosent necessarily mean whore, but a whore is a profligate. The adjective of it means "waste" and the noun of it basically means "filthy" in the same way that a whore is filthy. So when the Legion calls someone a profligate they are either calling them a waste of life or a degenerate. Also with the Rome thing, I think the Legion only adapted the military point of the Roman Empire and not the society part, since the Legion dosent really have a society, just one big army. Enslavement, crusifictions, beheadings, ect are primarily what the Roman military did, so it makes sense the Legion would try and mimic.