Based on current changes, wishlist for Disc
Rapture: Whenever you cast PW:S, you gain Rapture, restoring 2% mana every 3 seconds over 12 seconds. Non stackable - casting it again just extends the duration (but to no longer than 15 seconds.) PVE and PVP priests get the same amount back that can be more easily balanced and is not at the mercy of a long chain of missed hits on the tank. A buff is much more easy to monitor in game than an ICD so will help newer players.
How would we deal with AOE?
1. First we would pre-shield - but this would be our "Heal" type AOE. Too much pre-shielding breaks encounters and bores the hell out of our raid mates. Numbers based on my level 501-505 - http://eu.battle.net/wow/en/character/mazrigos/Jesinta/simple
Power Word: Aegis - Basically a POH clone, cast time, group targeted, but costs a little less say 12k) that puts DA on a group. The size of the DA would be approximately 15-20k per person. Approx 30-40k HPS and 6.25-8.33 HPM. (Similar to Kael's suggestion above)
2. Once the damage has been done our main AOE would be POH which would heal for roughly 30k for an average of 60k HPS and 11.11 HPM. Any criticals would still proc the 50% DA.
3. PW:S How to bring it in to the fold a little more than now, but not as much as it was in WOTLK . Reduce the mana cost to 13k and buff BT to encourage weaving. BT now increase Haste by 10% for instant and channel spells for 5 seconds or until you cast a cast time spell. Whenever you cast a cast time spell, increase the Haste bonus by an additional 10% and the spell gains an additional 10% chance to crit.
Also, PW:S now scales with Crit, increasing the shield by 50% of your crit rating.
4. When under the effect of Borrowed Time, your POM will auto bounce (á la Holy DI)
PW:S > POM (gets Holy DI treatment and 10% haste > Penance (10% haste) > Prayer of Healing (25% Haste and 10% Crit chance). This way, BT is less powerful for PW:S spamming and encourages more spell weaving.
5. Spirit Shell remains a 1 minute CD but with 4-5 charges. Each FH/GH/POH consumes one charge and takes the core FH/GH/POH heal amount and turns it into a SS shield and then increases that shield by your crit % (+11% say) and then increases the shield by your Mastery value. This is definitely a throughput boost, no denying it, but I really feel our absorption spells have to be improved by our Mastery stat. Whilst this is a powerful increase, progression oriented Priests will still use this calculatingly and not just macroed in.
6. Penance increased by an additional 20% and the CD is now 8 seconds baseline. Now shoots out 6 bursts of healing rather than 3, The machine gun would be epic graphically and when used offensively it is an improved AOE tool.
7. This would mean for AOE we have PW: Aegis for relatively weak prevention, POH for healing up after the damage as well as BT infused POM, 6 pulse Penance Atonement and the level 90 spells. Our POH/POM/Penance on balance would be 70% of the power of the other healers' tools, but the pre-shielding of PW: Aegis would make up the rest.
8. Whenever you cast Atonement proccing spells in PVP, the Atonement heal is calculated before resilience is taken into account - so that the size of a PVP Smite heal is of the same ratio to the size of regular Heal as it would appear in PVE. Same goes for MWs who want Fistweaving back.
9. PW:S Dispel protection - whenever PW:S is dispelled the, the dispeller's next damage abilty used deals no damage and instead places a Divine Aegis equal to 10% of the targets max health instead. If the dispeller would next cast a heal, no healing is done and instead a healing absorption shield is placed, consuming healing equal to 5% of the dispeller's maximum health. Or if the dispeller is a healer, all healing spells are locked out for 5 seconds, if a dpser, all damage spells are locked out for 5 seconds.