I don't think Blizzard should make such a drastic change without giving us another AoE healing tool like they promised with this expansion. They first told us they were removing PoH from Disc and that Holy Nova would be our main AoE healing tool. But then they never showed us anything substantial (I think they honestly believed we'd run around like fools spamming Holy Nova) and decided to scrap the idea.
When our level 90 talent and SS are on cooldown, the only thing we can do to AoE heal is PoH and Atonement heal which isn't very effective. If they want us to use something other than PoH to heal the raid then give us something new and fresh because PW:S and Penance aren't going to cut it.
Here are some possible ideas to get Blizzard's thoughts rolling. Feel free to comment on my ideas or post your own. All of my ideas but one have a heal/absorb component that would help us AoE heal but would also benefit from our mastery. Also unlike Spirit Shell, these spells are meant to be reactive rather than proactive, which would compliment us with other healers rather than reduce their roles.
Prayer of Refuge - 10 sec cooldown - Instant Cast
Surrounds 4 of the most injured allies in a protective shield that absorbs X damage. Lasts 6 sec. When the shield breaks or its duration ends, the shield bursts healing all allies within 15 yards of each target for Y health.
Light Sear - 5 sec channel
As a Discipline Priest, your Mind Sear becomes Light Sear. Causes an explosion of holy magic around the target, causing X holy damage every 1 sec for 5 sec to all enemies within 10 yards of the target and Y healing every 1 sec for 5 sec to all allies within 15 yards of the target.
Renewed Hope - Instant Cast - 8 sec cooldown
Sends 5 of the most injured allies Renewed Hope for 8 sec. Renewed Hope grants the target an absorption shield of X every 2 sec. After 8 sec are up, the target is healed for 100% of the remaining shield.
Orb of Lights – Instant Cast – 15 sec cooldown – 30 yard range
Places a holy orb on the ground healing all allies within 30 yards for X every 2 sec for 8 sec. After reaching the end of its duration, the orb explodes granting 6 of the most injured allies within 40 yards a shield which absorbs Y damage.
Power Word: Sanctity – Instant Cast – 20 sec cooldown
Causes your next Power Word: Shield to become Power Word: Sanctity. Power Word: Sanctity absorbs 25% more damage and instantly heals all allies within 30 yards of this target for X% of the absorption shield.