They should just give PLD some traits that enhance the CNJ spells they get. You have to have the class leveled to unlock PLD in the first place, and it's not like CNJ/WHM can somehow access PLD traits and abuse them.

Give a trait that doubles cure potency around level 40, or one that makes Raise combat-castable and doubles its cooldown or something. Maybe a damage spikes effect on one of the buffs but for the caster only.