Originally Posted by Sheshonk
Yeah I'm really curious as to why spirit is rated so high. I was under the impression int gave back roughly double the mana regen. I realize spirit grants SP as well, but that shouldn't make it as competitive of a stat as listed.
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Well, we can calculate this pretty easily. Mathing it out, I get the following:
Int gives us more mana in several ways:
* More MP from replenishment
* More initial MP, which we will represent by calculating the amount of MP5 we would need to recover the same MP over the length of the fight
* More MP from spirit regeneration with intensity
Spirit only gives us mana in one way, with the recent change to innervate:
* More MP from spirit regeneration with intensity
We also have to keep in mind that 1 point of raw int is actually worth more than that, due to Kings and IMotW. I'll, showing my work in case I make a mistake or omit something. Please point out if you see any mistakes in my math or assumptions!

int_mod is usually = 1.10 * 1.02
spi_mod is usually = 1.15 * 1.10 * 1.02
actual_int = int_mod * int
actual_spirit = spi_mod * spi
base_regen = 0.003345 (this is 0.6 * 0.005575 since patch 3.1)
mana_pool = int_mod * int * 15 + 3496 + mana_bonuses
MP5 due to replenishment: 0.0125 * replenishment_uptime * mana_pool
MP5 per int due to 80% uptime replenishment: 0.15 * int_mod
Equivalent MP5 per int due to increased initial mana pool: 15 * int_mod / (12 * fight_length)
MP5 from spirit regen: intensity_percent * 5 * sqrt(int_mod * int) * spi_mod * spi * base_regen
MP5 per int due to increased spirit regen: 0.5 * 5 * [0.5 / sqrt(int_mod*int)] * int_mod * spi_mod * spi * base_regen
= 1.25 * .003345 * int_mod * actual_spirit / sqrt( actual_int )
= 0.00418125 * int_mod * actual_spirit / sqrt( actual_int )
MP5 per spirit due to increased spirit regen: 2.5*sqrt( actual_int )*spi_mod*base_regen
= 0.0083625 * sqrt(actual_int)*spi_mod
To summarize, mp5 gained due to one point of int is
0.15 * int_mod + 15 * int_mod / (12 * fight_length) + 0.00418125 * int_mod * actual_spirit / sqrt(actual_int)
mp5 gained due to one point of spirit is
.0083625 * sqrt(actual_int)*spi_mod
Plug in numbers for the variables and you will see exactly how good int and spirit are for longevity at your current gear level. For example, at 1200 int / 1400 spirit, with kings, IMotW and Living Spirit, and an 8 minute fight:
MP5 from 1 int: 0.533211658
MP5 from 1 spirit: 0.373781198
So, under these conditions, 1 point of spirit is about 70% as effective as 1 point of int for longevity purposes alone. Of course, it's important to remember that Spirit also converts to spellpower at a rate of 1 raw spirit -> .193545 spellpower, assuming Kings, IMotW, Living Spirit. Since 1 point of spellpower is assumed to be equivalent in power to 0.8 MP5 (this is a reasonable point to debate), we should add 0.8 *.193545 = .154836 to the value of a single point of spirit. As you can see, this makes spirit very competitive with int (and even moreso if you favor SP higher than 0.8 MP5)