Demystifying Spirit Shell

Spirit Shell is a new tool available to Discipline in MOP. Essentially it allows us, on a short 1 minute cooldown, to convert all of our spells into absorbs that last for 15 seconds. Finally, we have a spell that lets us do what we’ve always wanted to do… mass absorbs!

This isn’t mechanically different than POH spamming to prepare a raid with Divine Aegis prior to damage occuring that many priests have been comfortable doing in 4.3. Spirit Shell now simply allows us to do this much more effectively, and with much greater ease. Note: Spirit Shell caps at 60% of the Casting Priest’s HP and each Disc Priest in your raid can cast a unique Spirit Shell.

Using Spirit Shell effectively will be a hallmark of a good Discipline Priest. You could simply use Spirit Shell on cooldown and either pad a tank, or POH pad a raid and see fairly positive results— however the real marker of a good Disc Priest will be using SShell when its needed the most. Despite it having a fairly short cooldown, we might want to pause a second or two to line up Spirit Shell’s absorbs to large raid/boss damage. Simply using the ability on cooldown will be effective, but ultimately not as effective of using it when the fight benefits from it. The tricky part is not delaying it so much, that the short cooldown is wasted.

Why is understanding Spirit Shell so important? Spirit Shell will represent a LARGE PORTION of your output on many/most fights… understanding its mechanics and stat scaling will be critical.

Spirit Shell scales exceptionally well from both Mastery and Crit. Each cast of a heal while Spirit Shell is active will be the same (barring throughput procs). The Spirit Shell calculation takes Mastery, Crit, and Divine Aegis creation into account and rolls it all up into a single absorb– making this one of our most scalable heals in our arsenal. Spirit Shell scales linearly by Mastery as well as by the amount of critical strike chance you have. Additionally, when Spirit Shell is active, it essentially ignores the RNG aspect of Crit as it provides direct scaling based on your critical strike chance (guaranteed). (It does this by essentially looking at Crit as an aggregate stat, not as a RNG stat based on a single heal)

Spirit Shell’s Calculation is as follows:
Non-POH Shell = Average Heal * (1 + Mastery %) * (1 + Crit %) * (1 + (Crit % * 0.30)) 
POH Shell = Average Heal * (1 + Mastery %) * (1 + Crit %) * 1.30

As you can clearly see, SShell’s stat scaling is quite liberal, scaling crit linearly with the amount it absorbs as well as mastery. This method of scaling essentially guarantees crit chance to provide scaling to the heals cast when SShell is active. (as well as accounting for Divine Aegis).— This method of scaling, in fact, is better than the baseline spell’s scaling  just by nature of Spirit Shell. In fact, it may be too good on a number of single target heals– be careful don’t overcap the 60% cap on SShell! Currently, a single GHeal gets you about 80% capped…. and with full stacks of Grace and a healthy amount of Mastery, you’ll likely get capped in a single GHeal cast.

Haste does not have a direct throughput increase to an individual cast of Spirit Shell, however it does allow you to cast faster while the Spirit Shell proc is active, and theoretically, create more Shells during a single Spirit Shell cooldown. Generally speaking, you should be able to fit in 6 GHeal/POH casts during Spirit Shell’s uptime. (some haste and spell conditions might allow for upwards of 7). Haste scales Spirit Shell in a tiered fashion, given the fact that you must complete the cast when Spirit Shell’s buff is active. If you cannot complete the cast when the buff is active, it is considered a regular heal. Once you get enough haste to complete that cast in the time allotted, then you can count it towards SShell scaling.

How do you make the most out of Spirit Shell? Know the fight. That is always the biggest boon to a Discipline Priest. The more you know and understand the fight, the better you can be at predicting periods of large amounts of damage and preemptively preparing the raid (or Tank) with Absorbs.

Spirit Shell does not scale with Archangel, so save this cooldown for after/before Spirit Shell is going to be used. Further, Inner Focus only provides the mana cost reduction when Spirit Shell is active. (this is intentional given how Spirit Shell’s guaranteed crit scaling is already accounted for). Remember to use, and time these abilities appropriately before or after a Spirit Shell period.

Generally, absorb mechanics are fundamentally superior to raw healing. This is because it actually preventsthe damage from happening to a player. If a killing blow is prevented via mitigation, regardless how much a player can raw heal, that mitigated damage is tops.

Editor Comment: Thanks to my friends Valen and Dayani for assistance in the TC and confirmation of calculations.