Base mana regen is 0.4% of mana pool per second. The above shows we will be spending more than that on anything we do. Holy Light spam has been said by Blizz to be a mana positive thing in entry level gear. At 550 Ilvl at level 100 we can expect 265+/- spirit without spirit trinkets. 570+/- with 2 trinkets. So the question is how much regen will those numbers get us, and as we complete tiers in WoD how much more spirit will we have? Will we ever hit 3%? If so mana will no longer matter.
My concern is Denounce dps does not look to be mana neutral as it is more costly than HL by 50%!