As a pure turtle tank, I think PLD (My main job, by the way) is quite boring.
The fun part happens when you try to be a little more than that.

As an example, let's take the Tonberry King. You can tank it straitgh up, with Shield Oath, using your cooldowns for grudge move.
Or you can tank it with Sword Oath to do far more DPS, pop Shield Oath for the first Grudge, go back to Sword Oath, pop Shield Oath and Rampart for the second grudge, and so on...When trying to optimize both your tanking and your DPS, that's when PLD becomes reaaally fun to play.

As a side note, I'd really appreciate a third combo to have a more complex rotation. And I think Sword Oath sould have a self-cure potency boost, so that the "conjurer part" of PLD wouldn't be totally useless.