Do you see that thread with the WAR DPSing Garuda? A smart PLD can do even more damage than that WAR due to a combination of Sword Oath, Circle of Scorn, and Spirits Within(a 250/300 potency attack on a 25/30s cooldown, off the GCD. Even just one of them is better than the BRD's vaunted Bloodletter[150 potency, 15s cooldown] due to swords having higher base damage than bows).

And if the main tank is about to die, they can Cover the tank and pop their mitigation cooldowns to save the raid.