It's become pretty clear that for the next couple of months, we've all become beta testers for the new trees and mechanics. Things are very fluid right now with regard to damage, talents and spells for all classes and specs so any advice given today may become completely inoperative tomorrow. It's a good thing to keep in mind moving forward from here.
I would expect PW:B to be fixed at some point although I've heard a few reports from the beta that the spell is better there given mastery and a very different damage environment than what you find in WoLTK WoW. It's possible that PW:B is a spell that really doesn't come into it's own until one is well past 80.
It's also pretty clear from reading forums other than the Priest forums at Zam that people don't know what to make of a lot of the changes, especially the various ongoing series of buffs and nerfs so there's a lot of bad information floating around. Best to be patient, do your own practical theorycrafting by going out into the world as it is and trying stuff out to find out what works and what doesn't.
I emphasize 'the world' as opposed to just relying on training dummies. My own class (shadow priest) is in the middle of a large...discussion I guess would be the polite word...about the usefulness of SW:D, which lately redefined as a true execute behaves quite differently depending on target health. That's difficult to test on training dummies that essentially, don't die.
So go have fun, play and share your thoughts and experiences.
Sorry for going off on a tangent from your original question. It's 9:00 a.m. here, I'm having my first cup of coffee and feeling philosophical.