Final thoughts is divine seal is still the best healing CD in game.
I'm not singling you out in saying this, and it's not directed at you in any way, but I'm not sure why people would expect any different. Synastry is more of a tank cool down than it is a healing potency CD, and since it's potency increase it tied to the "tank healing" portion, it faces the same choice that Assize has, in a way; you can choose to use it as a tank healing CD or a potency increase, but the CD is very long. In the same time frame that Synastry can be used twice, Divine Seal can be used three times. WHM healing is still the undisputed king of healing, and over the course of a fight it becomes more and more apparent; once people stop freaking out over the "on paper" numbers, they will realize this. WHM still holds the crown, just as it did in 2.0, as the best reactive healer.