01 November, 2007

Spirit VS MP5 : What's the real conversion ratio?

For Druids, in caster form (or Tree form) the standard exchange of MP5 for Spirit out of combat is:

1 Mana ever 2 secs = 4.5 Spirit

In MP5 terms this means:

1MP5 = 1.8 Spirit

However as casters in combat we're subject to the FSR or Five Second Rule.

Five Second Rule (from WoWWiki):
After a character expends mana in casting a spell, the effective amount of mana gained per tick from spirit-based regeneration becomes a ratio of the normal listed above, for a period of 5 seconds. During this period mana regeneration is said to be interrupted. This is commonly referred to as the five second rule.
What this means is that once you cast a spell, mana regen is effectively nil, barring additional gear bonuses and talents for the next 5 seconds. Luckily Druids have such a talent, in Intensity. Intensity gives a 15% of your out of combat mana regen while casting (under the FSR).

MP5 Bonuses
Items that have MP5 also continue to provide that much mana regen during casting. Regardless of whether you are casting or not, MP5 is a flat regen rate. Because of this, it is often considered more useful than spirit. Often this is the case.

Spirit VS MP5:
The age old question then is how much Spirit equals 1MP5, while you're in combat. Unfortunately the answer is not as easy as a simple division. The time you spend inside the FSR dictates how much Spirit actually gives you because inside the FSR you only get 15%, and outside of the FSR you get normal regen.

From various trials during raiding, I've settled on 75% as an average figure for time inside the FSR. In some fights I can drop to as low as 65%, and some fights as high as 90% but on the average non-progression fight, 75% is my usual figure. Whenever I'm evaluating a piece of gear that's the level that I rate any spirit on the gear at.

Maths Inc!

Now we get to the maths bit. If I spend 75% of the time under the FSR then for 25% of any given period, I have spirit regen at the 1.8 Spi = 1MP5 rate and for 75% of any given period I have spirit regen at 12 Spi = 1MP5 (12 = 1.8 / 0.15). To move this to a single formula, I again turn to WoWWiki's Mana Regen page for:

m = x mana every 5 seconds
p = % of time in FSR
s = spirit
k = regen while casting = .00, .15, .20, .30

To get spirit: S(m,p) = 1.8*m/(1-p+k*p)

Plugging in the Druidic figures to get Spirit:

m = 1
p = 0.75
k = 0.15

Spirit
= 1.8 * 1 / (1-0.75 + 0.15 * 0.75)
= 1.8 / 0.25 + 0.1125
= 1.8 / 0.3625
= 4.96

Therefore any item with 4.96 spirit on it, is the equivalent of a piece of gear with 1MP5 on it. Unfortunately, Blizzard doesn't budget like that when assigning Spirit to gear. 1MP5 is worth the same amount as only 2.5 Spirit on a piece of equipment. This is why for a long time, MP5 has been considered more useful than spirit when looking at gear.

Is that it?
Sounds simple doesn't it. For example, the [Hood of Primal Life] has 31 Spirit on it. Therefore under the above calcs, you get 6.25 MP5 don't you? Not quite. As a Resto druid we have to take other factors into account. Lets look at our talents first. I've already discussed Intensity, but there is another Talent that assists here.

Living Spirit increases your total spirit by 5%/10%/15%. Therefore 1 point of spirit on an item is really 1.15 points. So that 31 Spirit on the Hood becomes 35.65, and thus makes the Hood provide 7.18 MP5.

Back to the Maths
So if we get 1.15 Spirit for every point of spirit on an item, what's that mean for our 4.96 Spirit per MP5. It reduces it by 1/1.15 or 86.9%.

= 4.96 * 0.869
= 4.31

Is *that* it?
Yes, that's it. The magic number for Spirit to MP5 for a Resto Druid under a 75% FSR (heh what a mouthful of qualifiers) is

4.31 Spirit = 1MP5

If that's it why are you still talking?
Funny I should ask me that... In Patch 2.3 Blizzard will be adjusting Intensity (as well as all the Priest equivalent talent) so that it becomes 10%/20%/30%. This will catapult us back to the heady days of the 2-Set bonus from Stormrage before TBC, which means we need to re-evaluate our magic 4.31 Spirit figure.

More Maths Inc!
Ok so back to the pen and paper to work out the new number.

m = 1
p = 0.75
k = 0.3

Spirit
= 1.8 * 1 / (1-0.75 + 0.3 * 0.75)
= 1.8 / 0.25 + 0.225
= 1.8 / 0.475
= 3.79

With Living Spirit
= 3.79 * 0.869
= 3.29

Therefore, under Patch 2.3 changes to Intensity, the magic number for Spirit to MP5 for a Resto Druid under a 75% FSR (a bigger mouthful of qualifiers) is

3.29 Spirit = 1MP5

This brings us closer to the budgetary cost of 1MP5 = 2.5 Spirit, when Blizzard calculates item budgets.

If that's it, why get Spirit?
Since Blizzard under-budget's Spirit vs MP5, why would you use Spirit? For a Druid, the answer is varied:
  • Extra Mana Regen during burst fights: Some fights require you to do a large amount of healing during one phase, then minimal healing during another phase. In these fights your time under the FSR can drop as low as 55%, rendering spirit much more worthwhile than it's budgetary equivalent MP5.
  • You're a Tree aren't you? The Resto Druid's preferred form, Tree of Life, provides an additional healing received by each party member by 25% of the Druid's spirit. This means that a druid with 600 Spirit is adding 150 healing to each member of the party receiving a heal.
  • You're not giving Innervate to mages are you? In a raid scenario, Innervate is your spare stack of about 2-3 mana pots that you can gulp in one hit. Innervate increases your Mana Regeneration by 400% and allows its full potential to regenerate while casting. However the interesting note is that if you can stay under the FSR while you have Innervate on, you get the 15% mana regen from Intensity *as well as* the normal 100% mana regen, multiplied by 4. So as long as you keep casting while you Innervate you get 460% mana regen. And under 2.3 you'll be getting 520% mana regen. However, direct MP5 is not affected by this regeneration increase, so stacking on Spirit will give you a much better result from Innervate.
Additional Note: Something I didn't cover here was Blessing of Kings (BoK). In almost any 25-man raiding situation, Resto Druids should take BoK over Blessing of Wisdom. Assuming a properly geared Druid with a minimum of 500 Spirit before BoK (so including Divine Spirit), BoK gives you 50 Spirit. Yes this only translates into 12 MP5 instead of 41MP5 (48MP5 talented), but Innervate brings this to 53 MP5 during it's effect and the additional roughly 500 Health, +12Heal and 750 Mana makes it well worth the MP5 loss. In 25-man content too, you generally have at least 2 paladins in a well balanced group, so you should receive both.

To calculate the magic number with BoK included, simply multiply by 0.909:

Now
= 4.31 * 0.909
= 3.91

After 2.3
= 3.29 * 0.909
= 2.99

So, after all that, Blizzard aren't complete nubs! The 2.99 is much closer to the Blizzard budget of 1MP5 = 2.5 Spirit.

Welcome to Secret Tree Business

'ello.

I've never done a blog before but I've been reading a lot of recent stuff on other people's blogs about Warcraft and specifically Resto Druids.

My History:
I started playing WoW on the Open Beta, and pre-ordered WoW for its release. Day 1 I rolled my Mage on Silverhand's Horde side. A year and a half, and 3 level 60s later, I re-rolled Alliance side to get raiding since the Aussie horde population on Silverhand was too weak.

I rolled a Druid back when nobody played Druids figuring I could get better raid chances as a Resto Druid than a Priest. Since then I've played a Resto Druid almost constantly, doing MC and BWL from learning to farming with two different raid groups, including being Raid Leader for the second, and then on into the Burning Crusade. Since TBC's release I've done Karazhan for 7 months, and finally rid myself of that by transferring servers to Aman'thul to start raiding 25-man content.

Armoury Link

For this blog I plan to ramble about items, mechanics, and styles for a Resto Druid and other healers. But since I'm facing Solarian right now I should focus....

Later. :-)

2008-11-14 Addendum: Yes I posted 2 things then let the blog sit for a year. So sue me, I was busy playing Warcraft.... :-)