Blizzard has been talking about the issue with mage mana longevity for as long as I can remember. It has been a crucial issue for the class throughout burning crusade, specifically in PvP. Now, it looks like the class may finally be getting the buffs it has been asking for.
We think mages are still having mana problems and don’t want to reduce Evocation’s cooldown anymore. Nor do we want to buff mage armor too much more or using e.g. molten armor seems pointless.
Instead, we reduced the mana cost on Fireball, Frostbolt, Frostfire Bolt, Arcane Blast, Arcane Missiles, and Arcane Explosion. (source)
There’s been tons of changes during the patch 3.0.2 PTR, but I think this one eclipses them all. So long as an appropriate reduction is implemented this should solve many mana problems for the mage class. No exact value reduction has been announced yet, but I would expect to see a finalized version on the next PTR build.