Clememecy interferes with PLD's gameplay flow. Use it too much, you suddenly won't have at least 5k MP to execute entire spellblade combo during burst window. It also eats up a GCD. 1000 tank potency is about the same as today's WHM Cure II/Solace which suffice to say, isn't that much given its other costs attached to it. Definitely not as egregious as WAR's SiO regen (why, just why), BW (lmao), Equilibrium regen (zzzz) and Damnation (damn).