This has now been fixed.
Arcane Mage Guide
Arcane Mages are the only DPS spec that primarily uses mana for their DPS rotation. Mana management is a mastery point for Arcane Mages with many of their spells adjusting the mana cost of spells. Arcane Charges are generated by multiple spells including Arcane Blast which makes spells cost more, but will deal more damage so mana manggement is very important for the spec.
After the Weekly Reset, it appears that a hotfix has created a new bug in the game, reducing the passive mana regeneration for Arcane Mages to a negative value. This means that both in combat and out of combat, Arcane Mages are losing mana periodically, rather than gaining it back.
