Originally Posted by
Naraku_Diabolos
The class system is basically for solo play. See, you can be a MRD and then use Cure on yourself during a fight, but once you switch MRD to WAR, you can't use Cure. The jobs act as mainly a party-based system because you have your uses for when you are in a party, as WAR can both dish out damage and tank if needed. WAR does get Second Wind, but WAR has crappy MP so there wouldn't be a reason for it to keep Cure.
Right now my THM has a Wind Brand weapon, so I have Aero on it just for kicks and I can do bleed damage while soloing, but if I want to join a party I'll go as BLM and do my part by sitting back and nuking the monsters while the melee fight. The classes do have a purpose.