The players are what makes them unique. The ones who go above and beyond to master the class. The Bard who will sing for the group rather than just going "geewhiz! look at my numbers!" The White Mage who can make time to throw out an Aero & Aero II in between healing. I could go on but you get the picture.

Yes, the roles are all equal in theory. But it's up to the people playing them to make the most of it.