Spirit Shell: What Is It Good For? (Absolutely Everything…)

Just a note to let you all know I’ve updated my Priest spreadsheet again to reflect an error in my original calculations. I had assumed (without checking, bad Dedralie!) that the buff to Divine Aegis’ base absorption amount would also be reflected in the DA term of the Spirit Shell equation.

This is not the case. Spirit Shell still uses 0.3 for the Divine Aegis base absorption term, instead of the 0.5 just introduced in the hotfix. This makes Spirit Shell’s margin over the normal heal+absorb smaller than I anticipated in my spreadsheet. I have since fixed this, so the Spirit Shell calculator should now be accurately reflecting the in-game behaviour. See my Priest Changes page for more details!

I’ve heard rumblings that this recent hotfix has made Spirit Shell less valuable. Personally, I do not think this particularly devalues Spirit Shell. Yes, your normal heals will now be closer in magnitude (counting any Divine Aegis procs) to the size of their Spirit Shell equivalent. Spirit Shell no longer confers as much of a throughput advantage over straight healing. However, the strength of Spirit Shell is in negating as much damage as possible, and while the recent buff to Discipline Priests did not improve our capability to do this, it did not diminish it, either. But for a more in-depth look at how Spirit Shell performs compared to your usual healing …

… I have made graphs for you! The following graphs represent the influence that your Critical Strike chance and Mastery ratings have upon the amount of throughput increase you get from popping Spirit Shell.  I calculated these by first figuring out how much your Critical Strike rating and your Mastery (via Divine Aegis) increase your healing compared to the tooltip average healing value, and then working out the percentage throughput difference of Spirit Shell versus normal healing. This difference makes up the vertical axis; numbers above 0 indicate when Spirit Shell is a throughput increase, and numbers below zero indicate when Spirit Shell is a throughput reduction.

Note that these calculations do not include Archangel’s healing boost, nor do they include Inner Focus’s effects. This is because I don’t want to make assumptions about how the individual Disc Priest heals; some may only use Archangel during Spirit Shell, while others may use Archangel on CD, and possibly others still may not use it at all. Similarly, some may use Inner Focus with Spirit Shell exclusively, while others may vary their Inner Focus usage on a case-by-case basis. The only scenario which will make a difference in these calculations is if you use it during every Spirit Shell, but never use it outside of Spirit Shell, and all that happens is that Spirit Shell becomes proportionally better.

So, let’s get to the graphs!

Prior to the hotfix: Mathematically, it was possible for your non-PoH Spirit Shell to put out a shield that was smaller than the combined heal+Divine Aegis output of your normal healing. However, this could only occur for an extremely small window of ultra-low Mastery (as in, no Mastery on your gear at all and no raid Mastery buff) and ultra-high Critical Strike chance, neither of which is really possible to attain:

Pre-hotfix: SS vs Heal - non-PoH heals

Spirit Shell absorption versus (healing + Divine Aegis) for non-Prayer of Healing spells, prior to the Nov 5th hotfix. The red strip indicates values of Crit and Mastery for which SS constituted a throughput reduction. Click to enlarge.

It was impossible, however, for your PoH Spirit Shell to provide a shield that is smaller than the combined heal+Divine Aegis of your normal PoH healing:

Pre-Hotfix: SS vs Heal - PoH heals

Spirit Shell versus Heal size for Prayer of Healing, pre-Nov 5th hotfix. Click to enlarge.

After the hotfix: The benefit of using Spirit Shell over your normal healing has shrunk, but the throughput-reduction zones are similarly unattainable in current gear.

Post-hotfix: SS vs Heal - non-PoH heals

Spirit Shell absorption versus (healing + Divine Aegis) for non-Prayer of Healing spells, after the Nov 5th hotfix. The red strip indicates values of Crit and Mastery for which SS constitutes a throughput reduction. Click to enlarge.

You can see that the region where Spirit Shell underperforms your normal healing, for non-Prayer of Healing heals, has increased, but it is still limited to that extremely low Mastery and extremely high Critical Strike chance region, and we are unlikely to ever experience this in-game.

For Prayer of Healing, it is now mathematically – though not practically – possible for Spirit Shell to reduce your throughput; again, this is only in gear with extremely low Mastery values – so long as you have any Mastery at all on your gear, and have a Mastery buff in your raid group, you do not have to worry about this happening:

Post-hotfix: SS vs Heal - PoH Heals

Spirit Shell versus Heal size for Prayer of Healing, pre-Nov 5th hotfix. The red strip indicates values of Critical Strike and Mastery for which SS constitutes a throughput reduction. Click to enlarge.

So again, assuming that you are gearing for pretty much any Mastery at all, you are unlikely to encounter a situation where your Spirit Shell is not a significant throughput increase. It is undeniable, though, that it represents a much smaller throughput increase; for my guild’s Disc Priest, prior to the hotfix, popping Spirit Shell and spamming PoH represented a 39% throughput increase, while it now represents only a 15% throughput increase.

What does this really mean for you? In my opinion, this doesn’t really change much:

  1. Keep calm and carry on Spirit Shelling. It’s still a great throughput CD, it is affected by Archangel, and an ounce of damage prevention is still worth a pound of healing.
  2. What this change has done is simply “smooth out” the peaks and valleys in your healing throughput by raising the valleys. This is never a bad thing!
  3. If you want to maximise your Spirit Shell’s performance, focus on Mastery over Critical Strike chance. This was probably already obvious.
  4. I know how to make 3-D graphs now, so expect to see more of them :D
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7 Responses to Spirit Shell: What Is It Good For? (Absolutely Everything…)

  1. Derevka says:

    I might just have to hand over my tiara to you. ;)

  2. Derevka says:

    oops hit return too soon. But yes, youre spot on. Spirit Shell is always oging to be amazing (barring any MAJOR changes). I mean, lets be real here, its a button that lets you (provided you PLAN for it) say “Ok… damage stops NOW!”

    • Dedralie says:

      *blush* I have always wanted a tiara … but no! This is madness! I of course wouldn’t – couldn’t! – have done this were it not for you (a) alerting me to the DA buff to begin with, (b) pointing out that it doesn’t affect Spirit Shell, and (c) making me apply to SW, thereby raising my IQ lots by osmosis :D

      And yes, Spirit Shell is nothing shy of awesome. I will always value absorption over taking-the-damage-and-healing-it-back-up, but it’s hard to put an exact value on it. If Spirit Shell turned our heals into absorptions at half the efficiency, would I still feel the same? … Probably not. But shrinking its benefit from 40% to 15% by raising up our performance outside of Spirit Shell simply isn’t a big enough deal to devalue Spirit Shell IMO :)

  3. Valen says:

    I always love to see more priest theory crafting! Can you provide the crit/int/mastery for the purple point (or an armory link)? It is slightly different than my results. Specifically, reforged for Mastery>Haste>Crit, I don’t get a 15% difference; non-raid buffed, SS+PoH is about a 2% increase, and raid buffed, it’s about a 9.5% increase. For GH/FH, SS is a huge throughput increase, but for PoH, it’s much less pronounced.

    Also, taking the graphs all the way to 1.0 (which I assume means 100% mastery/crit/etc) is a little overkill I think it is reasonable to cap Crit at around 30% and mastery around 80% (which are both beyond what would be reasonable for the current tier or two). Not a big deal but I think capping the graphs in the realm of reachable stats helps ground the analysis more :)

    Nice graphs, though, and they match the rough conclusion I was coming to — the DA boost is awesome, and SS is still good, just not as zomg anymore. Which I hope was the point, as it is never fun to have such a huge disparity between a crazy OP ability and normal healing times, at least for something with a 25% uptime and short-ish cooldown.

  4. Dedralie says:

    Hi Valen (gosh I’m getting a lot of celebrities around here lately, it’s kinda freaking me out :P),

    I don’t know that I want to ‘out’ my guild’s disc priest (although it obviously wouldn’t be hard to figure out on armory), but taking raid buffs into account I calculated a 58.16% Mastery, 15.437% Critical Strike chance. My calculations are independent of the heal size so they should be accurate no matter how much Spell Power/Int you have. You can spot-check my math here and tell me where I have gone wrong:

    Using the equation (1+crit)(1+(DAbase*(1+mastery))H(tooltip) = (1+crit)(1+(0.5*1.5816))H(tooltip) = 1.15437*1.7908*H(tooltip) = 2.067H(tooltip) for PoH’s normal healing

    Compared to (1+crit)(1+DAoldbase)(1+mastery)H(tooltip) = 1.15437*1.3*1.5818*H(tooltip) = 2.37348H(tooltip) for PoH’s SS component

    I get (2.37348/2.067) = 1.1481 or a 14.81% increase in PoH’s throughput when used with Spirit Shell.

    What I think might be tripping us up – at least, it’s tripping me up a bit right now as I double-check on my own Disc Priest, who is not as geared as my guild’s Priest but at least is accessible to me – is that the “normal healing” equation includes a modifier for Crit because I’m looking for an ‘average PoH’ not a ‘this specific cast of PoH’ type number. This makes the calculated %increase from SS look smaller than it really is if we are comparing it to our own non-critting heal vs SS in game. Here’s what I mean by that –

    Same calculations, for my 7.63% Crit, 39.62% Mastery Disc Priest (Armory link):
    = 1.8277H(tooltip) for PoH heal+DA (this looks good. My Disc Priest’s H(tooltip) for PoH is 21506. This would give a theoretical heal+DA of 38678; in-game I got 36592 from a non-crit. If we remove the crit argument from this equation it’s simply 1.6981H(tooltip), which would give a theoretical 36519 – clearly matching up)
    = 1.9535H(tooltip) for PoH’s SS absorb (this is not working out exactly for some reason that I can’t determine. With a 21506 H(tooltip) I should see a 42013 SS absorb, but I’m getting a 41978 SS absorb, a 35-point difference that I can’t really track down. Maybe a rounding issue?)
    = (1.9535/1.8277) = a 6.88% theoretical increase of my PoH SS over my PoH heal+DA.
    If we remove the crit from the initial equation to compare a single non-crit PoH heal+DA event to its SS absorb equivalent, I get
    = (1.9535/1.6981) = 15.04% increase in the case of a single non-crit event. Of course since PoH itself has some variance I don’t expect to see exactly 15.04% every time – PoHes that heal for above average will reduce the apparent size of the difference.

    So how does this stack up to my in-game numbers? Well I got a 41978 PoH SS and a 36592 PoH (heal+DA). 41978/36592 = 1.1471, which is pretty close to the expected 15.04%, given that the PoH heal was slightly larger than the tooltip heal would have you expect *and* that I can’t track down the source of this 35-point discrepancy between PoH SS(theoretical) and PoH SS(actual).

    I feel kiiiinda confident that my method for calculating the %increase of using SS vs. not using it is robust. But if you find a flaw in my math please do let me know, I would rather be right and have to re-do my graphs, painful though it may be, than to be wrong :P

    As for taking the graphs to their extremes … I’ll be honest, I’m not very intuitive with maths, so I kinda need to take things to their illogical conclusion to work out a trend. These graphs do have some unrealistic numbers in them – it’s really not feasible to have less than 25% Mastery or enough Crit to put our SS absorbs as smaller than our non-SS heals – but I thought it was interesting enough to see that trend. I had intended to shade the range of “achievable/feasible stats in this tier” a different colour, but I can’t seem to do that within Excel itself, so if I wanted to show the “theoretically possible for SS to be a throughput reduction” data I kinda had to go with all of it.

    I’ll see what I can do about that via normal image editing…

    Thanks for stopping by, Valen, I appreciate you spending your time on my dinky lil site! :)

  5. Evigrof says:

    ^ ummm.. I like ice cream.

    Wow.. math is cool. Thank you for breaking this down. I used spirit shell with PoH but I wasn’t sure if it really was that much more beneficial. Just coming back from a hiatus and finding this info helps me figure some things out. Keep up the great blogging!

  6. Lorena says:

    “Spirit Shell: What Is It Good For? (Absolutely Everything) | healiocentric” ended up being a
    pretty pleasant article, . Continue publishing and I’ll try to keep on reading through! Thank you -Monte

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