The formula for regen based on spirit is going to change in next patch (at least it has on PTR). In short, the amount of mana regenerated based on spirit will increase based on Intelligence. It's too good to be true, but still worth dreaming.
Take a look at HealerLFG for superbly visualized info about the subject: News from the PTR : Intellect > Spirit Regen
(I love spreadsheets and graphs, such a great post!)
Some additional number crunching:
Source: Richelieu's post at Elitist Jerks:
MP5 | Outside 5SR MP5 | Inside 5SR
Live: 361 195
PTR: 480 237
Net Gain: 119 42
These values are for a holy priest with 3 points in Meditation and the PMC set, with no buffs, with identical gear and talents, Spirit of 359, and Intellect of 501:
Source: New Regen model (PTR) post at WoW EU PriestForums:
mp5 = 683.4 mp5
instead of :
mp5 = 406.25 mp5
Numbers with 600 int and 600 spi
Additional Info about Patch 2.4:
2.4 Test realm patch notes at mmo-champion
Patch 2.4 in WoWWiki
