Originally Posted by
Mokka
Think of spirit as hit. now suppose that int increases the hit you gain from hit rating aswell. with this in mind, hit rating would be more valuable the more int you get. you would get more hit from the same hit rating. this would make hit rating more valuable, each point of hit rating would mean more DPS.
But, when you reach the hit cap, there is no point in stacking more hit rating. the same goes with spirit, just because it gets more powerful, doesn't mean you need to stack it as much as you can. You only need enough to last the whole fight.
That's why you don't look at spirit's stat "weight" as you do to mastery or crit. You need to reach a cap, and that's it.
TLDR: Int increases the amount of regen you get from spirit, but you need only enough regen to make your mana last the whole fight. More then that is a waste.