So levelling mages who aren't frost now have one of their main means of defending themselves from incoming mobs removed. This won't affect raiding or instances, just a mage's ability to level.
Now betas are the right place to be experimenting with different game balance options, but this one is so bizarre that it's unfathomable. How did the design review meeting go?
Undercover Warlock #1: "The trouble with mages is that they're overpowered at melee range. Giving them armour that's almost as good as a warlock who has only a flimsy little voidwalker, sacrifice, demon armour, fear and drain life to protect him is just unfair."
Undercover Warlock #2: "Damn right! Nerf mages. We took away their water but they were still over-powered. Some of them survived fights with a mob their own level."
Mage class designer: "Errr... isn't that what all classes are supposed to be able to do?"
UW #1: "All classes ... except mages. Look, it says so here in the master game design document. See that bit in bloo... I mean red ink ... next to the typed bits? 'All classes should be equally balanced apart from mages, who are overpowered and should be be nerfed'"
Mage CD: "I'm sure that wasn't there this morning..."
UW #2: "Oh yes it was! I remember it very clearly. Nerf mages... that's the key message".
UW #1: "Look, let's be fair and take a vote on it. All those in favour of nerfing mages raise your hands ... and now all those against ... Well, that settles it then, two votes to one in favour of nerfing mages."
UW #2: "Next time we review them I think we need to take a look at how much mana they have. Some of them have been know to cast several spells in a row, you know."
Mage CD: "Heeelp!"
UW #1 and #2 in unison: "Muahahahaha!"
I'd love to know the rationale behind this change. It makes the game considerably harder for new players, without having any impact on end-game. Presumably it will get reverted once Azeroth is knee-deep in newbie mage corpses, but until then, perhaps it's time to try out a priest.