Mana is supposed to matter primarily for healers. The caster specs all have various mechanics to assist in mana regeneration, while the two mana-using melee classes have specializations that make it a complete non-issue unless they're using spells they're not supposed to use on a regular basis (ie, healing or casted damage). It's for this reason that we have other resource systems - Holy Power for Retribution, and totems/debuffs for Enhancement.

Totems, debuffs (Stormstrike and Searing Flames), and Maelstrom Weapon, that is.

You're coveting other classes because ours is over-efficient with mana?

We'll be nerfed eventually. In the meantime, bask in our glory!

Mana shouldnt be a problem for melee specs that have to use mana. Also, hunters don't have mana now so Enh Shammy gear has no stats now even remotely related to mana. In which case we'd be screwed if mana mattered.

Ret paladins and (I believe) enhancement shamans have had mana issues before, and it's simply left them as an unusable pve spec. A DPS class that runs out of gas a minute into a fight isn't particularly fun or good game design. Both Ret and Enhance is designed around cooldown limitations, unlike rogues or warriors. Applying a second limitation would be convoluted and pointless.