It's Spell dmg not power anyway i don't think you see that a 5 sec cast every 40-45 sec is a huge dps loss and RoP is a 1.5 sec cast without any haste and it lasts for 60 sec, yes you have to stay on it the hole time but i don't have any problem with that on very many fight besides spirit kings.
And about the PoM vs. Scorch personally i only use scorch on spirit kings because of the first boss where you have to stack