Hello, this is my first mmo-champion posting, so I hope the trolls don't find me too tempting. :P
"your Water Elemental restores mana to all party or raid members an amount equal to 1/2/3% of their total mana every 5 seconds. (Previously restored party and raid members health equal to 1/2/3% of their total health every 5 seconds.)"
Does the 44-point Frost Mage talent, Improved Water Elemental, result in Frost Mages being better mana batteries than Shadow Priests? Used optimally, I picture a Frost Mage parking his Water Elemental someplace safe for the full one-minute duration, thus restoring 36% of the entire raid's mana every 2.5 minutes* (*=read the Cold as Ice talent). By contrast to the raid wide Water Elemental buff, the 41-point Shadow Priest talent Vampiric Touch only applies to a single party.
This is strictly regarding 25 man raid bosses, where raid buffs are important and boss fights are long.
Please allow that talents are fluid, and that some who read this may see a different talent setup in the future.