We sort of had subjobs in ARR. If I recall, you needed CNJ to open PLD. Therefore, PLD could equip spells like Stoneskin, Cure and Raise (out of battle only). Warrior got Bloodbath from DRG. And I think MNK got Fracture from WAR. I don't know, it has been a while. But we sort of had subjobs. It was "ok." Some of these abilities had value. Many did not. They ultimately got rid of all of that and just went with role abilities.