Quote Originally Posted by Duelle View Post
BRD was turned from a song-spamming non-fighter into an archer with songs. WHM was turned from "Holy only" to "sort of like an elementalist but still heals". DRK was turned from "knight that hurts themselves to deal high damage" to tank.
A lot of that is a result of the original class system from 1.0 being adjusted to adapt to the introduction of jobs. Conjurer was originally an elemental caster while Thaumaturge focused primarily on light and dark with debuffs and healing.

When jobs were added, they had to associate them with a base class, but some of them didn't quite align well and got revamped. Bard got attached to Archer as there was no song-oriented class. Conjurer and Thaumaturge got their elements shuffled (and sort of got their roles reversed) to accommodate White Mage and Black Mage.