Akron

It's not only that. Fire Mages uses Molten Armor because they almost always have Shadow Priests (and even without, it's doable with Mana Potions) while Frost Mages are efficient enough to use Molten Armor even without a Shadow Priest. The only spec which currently benefits from spirit is Arcane, which also has the meditation talent. However, since the MSD change and the Fire/Frost buff, Arcane became pretty much obsolete. Nobody at a high level specs it. Considering Kalecgos is most likely immune to Arcane, Sunwell isn't helping either. So while potentially Spirit is useful for Mages (if combined with Mage Armor or Meditation) in real terms it is completely and utterly useless.

That said, I'm much more concerned about the lack of spell hit rating on Sunwell equipment. It creates a problem because Warlocks and Mages cannot really benefit from the new gear. There is a lot of spell damage, haste and red sockets - that's a very good thing - yet the lack of hit rating means one cannot upgrade to these pieces without using gimmick high-Hit items or gemming for Hit. It would be cool if the items were re-itemised to have more Spell Hit rating instead of the semi-useless high amounts of Spirit, for example.