Numbers apart, I think the major issue with red mage is the lack of cleave spells.

Every single class in this game has something that will increase their dps if there are 2 targets to hit instead of only 1, be it ST rotation skills that deal aoe damage or multi-dot. RDM has none of those. They really should make verflare/verholy AOE and even so I still think the cleave capabilities of the RDM would still be the lowest in the game.