Wrote this for my guild forum, thought you might enjoy losing 10 minutes of your time.
I have spent some time going through the growing pains of healing as a disc priest. While simply using your three major heals can be enough to do the job, disc priests have many other tools that can benefit both the tanks and the rest of the raid group. Proper selection of the appropriate spell is key to successfully healing as a disc priest.
First off, PW:Shield is your best friend. The true strength of discipline healing is not recovering lost health, but reducing or absorbing damage. Tanks refer to this as mitigation. Tanks rely on parry, dodge and misses to nullify incoming damage, but sooner or later, the boss is going to land some shots. This damage is reduced by mitigation. While each type of tank has their own mitigation (armor being the common factor), there are some healing talents and abilities that add to or complement their mitigation.
PW:Shield and
Divine Aegis: While PW:Shield is widely known for its immediate 5-9k bubble (proportional to your Spell Power). Divine Aegis is its lesser known counterpart. On a strict tank healing assignment, a disc priest can absorb more through DA than PW:S. While PW:S is available every 15 seconds, DA occurs on every heal that crits. 30% of the heal is turned into a mini-bubble that can stack up to 10k (cumulative with PW:S). This means that crits that would normally be wasted into overheal are now converted to absorption.
Inspiration: A holy talent that should be included in all priest healing builds. (Resto Shamans have a similar talent in
Ancestral Healing). Its description is self-explanatory. Reduce physical damage by 10% when you crit. Note: Magical damage is not affected.
Renewed Hope: This is a pleasant side effect to casting PW:S. Not only does the target receive 3% reduction in damage, the whole raid group receives the buff. There is no time during an encounter when this buff should be allowed to fall off the raid. If you are not casting PW:S at least every 20 seconds, you're doing it wrong.
The last bit of mitigation that a disc priest brings to the table is
Pain Suppression. It's relatively short cd (coupled with
Aspiration) makes it available for multiple uses for the longer encounters. It can be used to supplement the tank's own cd's for high damage portions of fights. It also can be used for emergency situations when damage needs to be averted and a direct heal is not a real option. PS plus a 7k shield can be cast on the run and provides around 12k mitigation/absorption.
So why cast PW:S if you don't need to? Perhaps your direct heals are enough to counter any incoming damage. Well, in addition to Renewed Hope, the disc version of PW:S also includes another tasty effect called
Rapture. Not only do you reclaim mana for your own pool, you give a little boost to the target's power source as well. It can happen only once every 12 seconds (except under a probably buggy situation where all shields are consumed simultaneously), and it isn't a major return, but over the course of a fight, it adds up for you and others. PW:S also produces
Borrowed Time which greatly reduces the need of gearing for haste.
Penance, Flash Heal and Prayer of Mending: The bread and butter of a disc priests healing ******** each of these have their own particular niches.
Penance is the highly visible, single target heal that sets disc apart. It is a channeled spell that delivers the first of three heals almost instantaneously to the target. (While most people consider the first heal instant, it does have an air time component, much like offensive spells such as a mage's Arcane Missiles.) It benefits from but does not consume the haste buff from Borrowed Time.
Prayer of Mending is a reactive spell that heals after the target takes damage and then jumps to a nearby, lowest health target. It is a smart heal in that given 2 targets in range to jump to, it will always jump to the one with the lowest health percentage. It can heal five times before it is consumed. If it is fully consumed it is one of the most efficient heals in the game, both mana-wise and time-wise. It often is not fully consumed as it should be kept on cd as much as possible. Normally cast on the tank, it can alternatively be cast on other clumped up groups that are taking regular damage. As long as you hear it bouncing around, it is doing its job well.
Flash Heal is normally considered the filler heal for disc, to be used when other spells are on cd and the target has the Weakened Soul debuff (the 15 seconds after PW:S is cast on a target). One notable exception is when you have tanks at low health. Due to the talent
Imp Flash Heal, a steady stream of Flash Heals at tanks during these periods results in more crits which leads to more DAs. Once the target stabilizes above 50% health, FHeal returns to its role as filler heal.
I haven't mentioned Renew. Normally Renew is not an ideal spell for disc. It is unable to crit and does not have the power that other disc heals have. Normally there is a better choice than Renew. Of course there are exceptions. When you come across them, you will know. Keeping Renew rolling on the tank is normally a good idea.
Disc does have its group heals. Prayer of Healing and Holy Nova provide less than stellar group-wide heals. Holy Nova is instant but is burdened with an incredibly small aoe (10 yds from caster). PoH has a larger radius (30 yds), can be targetted and has a decent healing amount, but it is long casting and quite mana intensive. It should be used with BT when possible and is a candidate for Inner Focus.
Divine Hymn is the ultimate "Oh crap" button. Its massive mana cost and long cd make it less attractive, and many priests often overlook it or forget about it, but it is the single-most powerful heal in the game. It consists of channeling for 8 seconds (can be affected by haste), has a range of 40 yds, can affect up to 12 different targets, will crit and does produce DA bubbles. It is a smart heal and has the added benefit of granting 10% more healing to all who are healed by it for 8 additional seconds. This means that the other healers benefit from this as well. This spell should be used with Inner Focus, if possible, as the benefits are most fully felt with it.
Other disc utilities:
Power Infusion: Can be used on self, but normally cast on a dps caster to increase their output and efficiency.
Hymn of Hope: This (as well as Divine Hymn) is an ability that disc and holy share. It regenerates a moderate amount of mana to raid-wide targets. While it does work off a percentage of your mana pool, it gives you a 20% boost to your pool during the channel. If used in conjunction with other % based mana regen abilities concurrently (such as shadowfiend or mana tide totem), all the regen is boosted accordingly.
If you haven't noticed, crit plays a large role in a disc priest's gear. Normally healers play a balance game between crit and haste. Since PW:S is so attractive for a disc priest, many of their casts will be hasted by Borrowed Time. This lessens the budget for haste on disc priests' gear. At 11% haste with full raid buffs, a disc priest's Fheal is reduced to a 1 second cast with Borrowed Time in effect. More than 11% haste is not wasted on gear (you cannot expect to be able to squeeze a PW:S in between every heal), but it is considered a soft cap for haste in regards to a disc raiding spec.