Strickly speaking the titles those characters have were the actual names of the Jobs they held from where they came from. Paladins, White Mages and Black Mages didn't exist there but there were disciplines that were similar and hence those names.

That said, a title is just a title so I don't know how much difference it makes. Strickly speaking though, referencing those characters, our characters aren't actually those things regardless of having mastered a very similar martial discipline.