A White Mage casting Fire does not do as much damage as a Black Mage doing so, a Paladin casting Utsusemi does not get as many shadows as a Ninja, a Red Mage using Curing Waltz does not heal as much as a Dancer, and a Scholar using a summon does not get as strong a pet as a Summoner.
A White Mage casting Refresh gains as much MP as a RDM. A BLM casting Haste grants the same attack speed bonus as RDM. A WHM using convert is as potent as a RDM using convert. Healing specialist job gets high level enfeebles like Addle but enfeebling specialist doesn't get healing spell since level 48 :/