Let's discuss Red Mage

[Xikeroth]

This would make the most since. Doesn't WoW also do this?

The majority of classes in WoW can perform multiple roles but only one at a time. Say you have a class that can Tank DPS and heal, they can't do so all at once. They are locked and even their skills change when they change from one role to another. So if they went from DPS to Tank, their tanking ability would skyrocket but their damage would drop a fair amount. Now while DPSing in that regard you will still have skills that can heal (and heal for a decent amount as well, nothing to be shrugged at) But they can't outdo their healer counterparts and tend to run out of MP very quickly.

There is nothing stopping SE from copying say... WoW's Paladin for Red Mage (with clearly RDM-based skills) with the ability to tank heal or dps, but you'd only be able to do one at a time.