However, says Ghostcrawler, they didn't want to reduce the cooldown on Evocation anymore, nor did they want to make Mage Armor so powerful that other Mage armors were no longer worth using. Thus, they simply lowered the mana cost on Fireball, Frostbolt, Frostfire Bolt, Arcane Blast, Arcane Missiles, and Arcane Explosion.
Of course, we still won't know exactly how much until the next build hits the Beta servers, but it seems like it's got to be good news if it's anything of a significant cost reduction. Of course, some Mages are still hoping for a more active mana regeneration mechanic such as the Warlock's Life Tap, but in the meantime, hopefully this reduction is enough to make a difference.
[Thanks to VyseV1 for the heads up!]