What really needs to change:
1.) Divine Aegis is underwhelming. It literally takes me a good MINUTE to pre-stack aegis to max before a pull. PoH needs to put a bigger DA per cast or have a much higher crit rate.
2.) PW:S is a piece of crap now that rapture is gone. Just look at how clueless Blizzard has been with this spell just since the beginning of cata. Cata comes out, PW:S costs about a billion mana so ppl complain and Bliz responds by drastically reducing the mana cost. Leads to people just bubble spamming. So Bliz ups the mana cost. People go holy and spec into bubbles in the disc tree and just bubble spam. Bliz hotfixes that a day later. Things are okay. Bliz says, hey f*k you priests here's 4.1 we're reducing the duration of PW:S from 30 seconds to 15 seconds. Oh, but DA will now last for 15 seconds. Our window of effective pre-shielding got cut in half that day. Now, on top of all of this, they take away Rapture and replace it with this garbage can spirit based system. Because you know, they want all healers to value spirit highly. And they don't want certain healing classes to have much better mana management systems. Ha! What a joke. FIX RAPTURE.
3.) Spirit shell, although pretty awesome in and of itself, is too damn clunky and takes too long to stack up. We already had spirit shell. It was called Divine Aegis. With Spirit Shell it feels like you took Divine Aegis and renamed it "Good Divine Aegis for 15 seconds."
4.) You got rid of Divine Hymn for Disc because it's too many CDs? Are you kidding me. We have barrier and PoH for raid healing. That's it. Bliz pretty much admitted they had no idea what to do for disc AoE healing. Remember they wanted to make Holy Nova our AoE heal and have it proc DA? Yeah, they tried really hard for like 2 weeks before giving up on that. Now we have the same AoE heal that holy has, which we have to spend an extra 25k mana or so via HF or Smite to get a 5 stack of Evangelism to have it heal an extra 15%. Oh, with no mana back when we pop it. Cool! Meanwhile holy gets to raid heal with CoH, PoH, HW:S, Divine Hymn and our 90. Resto Druids get 3 MIN TRANQS LOL, Wildgrowth, Tree Form, Swiftmend. Shamans get CH, Healing Rain, Healing totem, and Spirit Link Totem. Hpallies have whatever the hell they have I don't know I don't play a damn HPal.
Blah! I'm so sick of writing this and just ending here. I sound angry because I am. Blizzard's shown their incompetence with this class since well before the beta, and just made us completely useless to start off this expac. There is absolutely no reason to take a disc right now. And don't even give me "But PW:BARRIER LOL!" when there's a DK popping a 75% reduction barrier on a lower timer. Where's the non-spell damage barrier uses this tier? Are there any?