Hi all... long-time reader, first time poster. Somebody hold me.

I've taken the plunge because I have a some theorycraft to put forward (which involves what I think ought to be a more complex analysis) and want some intelligent thoughts on the matter. Please note that my spec is horrible and my gear is horrible and I'm in a guild consisting of some RL friends. How the following might actually pan out in the real world is, in fact, something I'd love advice on

Here is the original post (from another forum) that prompted my line of thought:
So there's a fair bit to take into account here. Firstly I looked at all the talent things mentioned and ended up with this spec: http://www.wowhead.com/?talent=rxMRzZZxGgkMtRhtEo

The next step was to work out spell rotations. Since I don't raid, I'm not sure how possible it is to cast 'perfectly'. After trying to come up with some rotations, I came to the conclusion that a rotation is impractical anyway, because our DoT times and cooldowns are all of different lengths (and not always multiples of the GCD, either).

So I settled on a different system:
I took a length of time, 2 minutes.
I worked out that for a all-spells rotation:
- 5 SW:P castings are required
- 8 VT castings are required
- 13 MB castings are possible (1.5s cast + 7.5s cooldown..? Or does the cooldown begin at the start of the cast.)
- 10 SW castings are possible (12s cooldown..? Or do I need to add the 1.5s GCD as well?)
- 22 MF castings are possible (Casting all the above takes 54 seconds (1.5s cast time/GCD each), leaving 66 seconds in which to cast MF)

Is analysing it this way workable? I have no idea whether, in 120 seconds, you actually CAN cast all that... but it didn't seem unreasonable. Moving on:

The math for working out how much mana is spent, how much damage is dealt, how much mana is subsequently returned, and how much is regenerated due to MP/5, is... relatively simple.

I assumed that the bonuses from Shadowform, Shadow Power, etc. etc. were additive, not multiplicative, but were factored after gear. Giving a 1.53 modifier to spell damage. Is this correct? I can also imagine that, for example, Shadowform and Shadow Power might add, and then be multiplied by the addition of Shadow Weaving and CoS. Or whatever. I'm sure someone knows.

To account for +damage, I used a 0.572 modifier for MF, 0.429 for MB and SW, 1.47 for SW:P (incl. the talent for extra ticks), and 1.0 for VT. I grabbed the base damage/mana costs of the spells from WoWHead, again allowing for talents.

Then, after all the adding/subtracting/multiplying via a spreadsheet, I found the following:
Damage/second: 1017.15
Mana spent/second: 155.32
Mana returned/second: 50.86
(And 6 mana/second from MP/5)

So, with 8500 mana to begin with:

t = 8500/(155.32-50.86-6) = 86.33 seconds until you're OOM.

So far so good, although I've not taken into account the unavoidable 1% resist rate. Advice on this? Doing the same calculation for other rotations is equally easy.

The thing is, I don't really know where to go from here to answering the OP's question. Say he uses a potion that lets him DPS for another 40 seconds. This brings him to the 2-minute mark, and would allow him to use ANOTHER potion. But only if the first was drunk to full effect in the first 6.33 seconds. Feasible? How would you analyse this sort of thing (Shadowfiend as well, although I didn't want to go there... variable returns based on it dying, your +damage, etcetc. Ugh.)

It's all multiplicative, after +damage is factored. That's what makes it so awesome. You'll want to revise your damage output and subsequent mana return.

Don't forget to factor in 41 mp5 from Blessing of Wisdom, 10 mp5 from enchants, and 16 mp5 from Elixir of Major Mageblood. This adds to 67 mp5, which is a decent chunk of the deficit you're running.

Thanks Exactly the kind of info I wanted. I'll re-run the numbers in a minute (waiting for downloads... snore... I wants to playyy!)

Problem is I don't know which of these (if any) were already counted. Well... obviously not BoW, and I'm guessing not the Elixir either. I might look up the base spirit, convert to MP/5, etc....

Ok. Now following:
Spec: http://www.wowhead.com/?talent=rxMRzhZZxGxkMxRhtEo
Gear:
- 1000 shadow damage
- 10% character-sheet crit chance
- 16% +hit
- 156 spirit (i.e. base spirit)
- Vitality and Restore Mana Prime enchants
Buffs/Debuffs:
- Full Shadow Weaving
- Curse of Shadows
- Misery
- Blessing of Wisdom
- Prayer of Spirit
- Elixir of Major Mageblood

I also corrected a few errors I'd made in the spreadsheet

And I came up with:
Damage/Second: 1123.93
MP/5 Return: 280.98
Time to OOM: 105 seconds

New numbers! Yay! Still don't know what to do about: resists, mana potions, shadowfiend.

Shadow Priest DPS Spreadsheet
Not updated for 2.1 but tweaking so as to account for SW increased cooldown and shadoweave decreased percentage is no big deal...