That's my concern too. Discipline even has two talents that reduce the cooldown of inner focus and the length of weakend soul upon using greater heal and heal respecively. Both of course completely useless in pvp. As disc in pvp I was mostly spamming flashheal waiting for penance to come up again, while as holy I pretty much never needed to cast a casttime spell. Renew chakra + getting 2 hots (+third from mastery) on people, together with prayer of mending, holy nova spam, and body&soul is awesome right now in pvp.