One of the biggest changes that all healers need to adjust to in Mists is the change to our mana pools, and the impact that will have on our regen. In case you missed the details: Intellect will have zero affect on our total mana pool, and primarily will be used in our Spell Power calculation and Critical Strike calculation. One more time to be clear: regardless of the amount of intellect you have, you will always have the same size mana pool, it will not increase.

At 90, all Priests will have a total mana pool of 300,000 regardless of intellect. Spells will now cost a fixed percentage of total mana (changed from Cata’s “% of base mana”). This is means if Greater Heal costs you 6.6% mana (or 19,800 mana at level 90), it will always cost the same amount regarless of gear level. This addresses and interesting issue that Blizzard has always struggled with: mana cost scaling as people gear up through tiers.

Remember hitting 85 and realizing that the one greater heal you just cast seemed to cost 20% of your mana pool? Well, thats because they needed to balance mana costs so the cost scaled with gearing. Look at yourself now in Cata, probably walking around in Dragon Soul gear… one greater heal is a fraction of your mana pool. Well, in Mists of Pandaria that cost is going to feel the same at just hitting 90 and being geared to the teeth in full T14 gear.

This also impacts how we look at our regen as well, and means that mana regen abilities that used to scale with our gear will not do the same in Mists of Pandaria. Take Shadowfiend for example: Shadowfiend restores 3% mana per swing. Well, in Cata this 3% scaled as your mana pool got bigger, increasing the value of Shadowfiend’s regen as you geared up. Well… in Mists, it will still be 3% per swing, however since our mana pool will not increase that 3% per swing at Level 90 is 9,000 mana per swing. That is 9,000 mana as a fresh level 90 in quest greens, or in full Tier gear. The same logic applies to Hymn of Hope, Innervate, and all the other “percent of mana” restorative abilities.  Since these are now essentially fixed amounts of restoration, you can think of them similar to a Mana Potion: a flat amount of mana you will get back that does not scale.

What does this all mean?

Well, it means we have to look at mana a bit differently. It really will become a finite resource and the way we look at our pool will be the same regardless of gear level…. until we layer in regeneration. Aside from our static regen abilities (Shadowfiend, Hymn, Mindbender, and Mana Potions) we will have spirit based regeneration. As of the latest beta build the spirit regeneration while in combat is provided by Meditation.  Holy and Disc have their own versions of Meditation (Currently, both Holy have 50% of their spirit based regen, continue while in combat), while Shadow does not have a spirit based regen model while in combat. (their primary regen is through Vampiric Touch).

This means, Disc and Holy will need to look to Spirit as their go-to stat for regeneration.

Every priest, regardless of spec, spirit level, or combat status will have an innate baseline regeneration amount. This is 2% of Total Mana every 5 seconds. After backing into the ratio in the charsheet, Spirit, is worth 1.1287 MP5.  This then allows us to back into our formula:

Combat Regen = Total Mana *0.02 +(1.1287*SPI*Meditation%) 

Now that we have our formula, we can take a look at how spirit as a stat will scale for both specs. Baseline, they have equal regen based on spirit. However, it is important to note that Disc still has the Specialization ability Rapture. Putting my personal feelings about this ability aside, Rapture now creates a really tricky balancing act for the developers to keep Discipline’s mana in check.

What Rapture provide’s Discipline, isn’t necessarily “regen”, but when Power Word: Shield is used on Rapture’s cooldown, it provides a Shield at a very reduced cost. This is because when the Shield is fully consumed, the priest is restored mana based on their total spirit… essentially providing an exceptionally mana efficient shield.

At 90, with Inner Fire active, PW: Shield costs 6.1% mana or 18,300– with 10,000 spirit, attainable in the first Tier of MOP raiding, Rapture restore’s 15,000 mana, which means this shield costs 3,300 mana. Exceptionally efficient– regardless of how much it shields for.  From a scaling perspective, this could put Discipline at a marked advantage, providing them with a “free PW: Shield and additional regen” once they reach 12,200 spirit. (The point where Rapture restores the full cost of PW: Shield)

Scaling

Since Combat Regen scaling is so single stat-linear now (unlike in Cata it had interaction with both Intellect and Spirit), depending on the total amount of spirit available on MoP gear, there WILL come a cross over point where there will be threshholds on where spirit will be devalued. (there is in the Cata model as well, but its less evident given that it moves based on two stats vs MoP’s single stat)

Its actually pretty easy to model since you know how much MP5 a finite amount of spirit restores, and you could make mana consumption assumptions. Its one of the downsides and follies to having total mana and the per point value of spirit equal in Quest Greens at 90, and Full Epics at 90.

Conclusion

The take away for everyone is:  Spirit will play a notably important role for both Disc and Holy’s mana regen model. Now, spirit, while not a direct throughput stat like Crit, Haste, or Mastery… it does provide indirect or “pseudo throughput” since you will have more mana regenerated, and thus will be able to cast more spells.

This will be different than what Disc priests  have been used to up until this point, who have always looked at Intellect as their go-to stat… However, ultimately, this new model could result in balance cross-tier if they can balance how fast Spirit/Spirit Regeneration scales in the long term. I do have some concerns that upper tier will result in so much spirit based/innate regen that this balance could tip… but time will tell.

Editor’s Comment: Updated as of 8/28/2012