spirit v mp5, post 2.3, with flourishes.
The problem with comparing spirit to mp5 – for priests – is that you’re potentially comparing apples to apple pies. Potentially, that is, if you’re using IDS and/or (Spirit of Redemption or Enlightenment).
SoR and En can give you (up to) 5% more spirit. In other words, every point of spirit on gear becomes 1.05 spirit on your character. And IDS adds +healing (and +damage). I will do a post, someday, on mp5 vs +healing, but I’ll say right now “it depends”. It depends on YOUR spell pattern and such. I will give a SWAG (scientific Wild Ass Guess) at 10 +heal = 1 mp5 – using Phaelia’s original post as my basis and 10 as a simplification of the 11 over there. To keep my head from exploding when I look at the new meditation, I’m going to ignore the healbonus to mp5 effect for now.
What this means is 1 additional spirit is .2625 mana every 2 seconds, or .525 mp5. Actually, adding the mp5 for the spellbonus effect and it’s .625 mp5 – two spirit are 1.25 mp5. Something that needs noted, of course – the healbonus is effectively an IFSR effect.
Now before we go on, let’s remember the nominal tradeoff by Blizzard’s gear options for spi:mp5 is ~5:2. But with all the wiggles I’ve mentioned, 5 spi is “really” worth 3.125 mp5. Which means in a perfect OFSR world, 1.6 spirit == 1 mp5. What we all know is that, well, perfect OFSR is impossible in combat. So…
One more data point, and we’re ready to seriously work on deciding between things. That’s the question of what we get from spirit under meditation 3/3. 30% as of this new patch – but only of the actual mp5, not the healbonus. That gets added on as a ‘constant mp5 analogue.’ 0.525 * 0.3 = .1575, + 0.1 (healbonus equivalent) = 0.2575 mp5. Again, that’s with 5% spirit bonus and 2/2 IDS — if you don’t have all that, you’re not going to do as well.
The critical final element is your dance speed. How much time do you spend in and out of the five second rule? If you know that, you can determine what YOUR mp5 tradeoff might be. Here’s the way it works:
% of time IFSR * IFSR rate + % of time OFSR * OFSR rate = mp5 per single spirit.
Since my heavy dance rate is around 70% IFSR, I get: (.7 * .2575) + (.3 * .625) = 0.36775 mp5 per spirit. Divide 1 by that number and it tells me my personal tradeoff is about 2.7 spirit per mp5. By the way, the “magic blizzard breakeven” in this case is so close to 65% IFSR (.3996875 mp5 per spirit) that it lets me close with a bottom line.
Blizzard’s magic line of 2.5 spirit per 1 mp5 for most gear options appears to be based upon a 2/2 IDS, +5% SPI priest being IFSR 65% of the time. There are a crapload of caveats in there, so bring your own salt lick.