PLD at the time only had Flash while DRK and WAR had Overpower/Unleash which meant they contributed more damage to killing adds faster, while PLD only had Circle of Scorn every 30s. Flash did 0 damage but just reduced damage a bit. To fix this, they gave PLD Sheltron on a shorter recast/higher duration, deleted flash, and gave them Full Eclipse/Prominence. Now PLD in additional also has Holy Circle, which I suppose they could add a Blind effect to if they wanted to make it flash-esque, but it's unnecessary.