I agree with this completely. No need to rigidly follow the roles handed out to us on the character creation process. If the fighting style suites you and your character in a rough way, feel fee to take the favored components and run with them. For instance, if your character is a hearty healer--PLD would also be the conclusion I would come to. Sure, you're more a tank when it comes to dungeon crawling, but ICly, you're a healer who can take some punches on the field, but who manly tends to wounds in-battle.
As Nahv'ir said, "Not everyone in the realm would be an adventurer or follow in the footsteps of combat. There have to be merchants, there have to be farmers, etc."
As an example, my character is primarily a merchant. I justify this by focusing heavily on my weaver/botanist jobs. BLM is not a primary identity, but it's something he dabbles in, has affinity for, and has talent for when things get hairy and people need more then their eyebrows singed.