Mages have been in a pretty good place from a design perspective, with each spec already fairly distinctive. As such, the changes to the various specs are a lot less dramatic than we've seen with Hunters and Priests. So let's take a look!
Arcane Charges will now be a secondary resource - they'll still work pretty much identically, but have a unique UI element.
The main change is that Arcane has a new Mastery, Savant, which increases Mana and Mana Regeneration. The idea here is that you'll have greater control over your mana expenditure. I suspect this means that you'll be able to spam Arcane Blast when you have cooldowns up, but you'll just have to conserve to prevent yourself from going OOM.
Arcane also gets a fun cooldown, Displacement, which removes the cooldown on Blink for four seconds.
Sample Talent: Quickening
This makes your Arcane Blast and Arcane Missiles stack up a haste buff that is removed when you hit Arcane Barrage.
They've effectively split the uses of Inferno Blast. The ability now simply is a guaranteed crit to help you get a Hot Streak.
Notably, Heating Up won't proc when you have a Hot Streak, so you'll be encouraged to simply let loose your Pyroblast when you can.
For cleave-AoE, Ignite will now inherently spread to other targets when it ticks, which kind of works thematically.
Combustion has been totally redesigned. It now increases your crit chance by 100% and adds Ignite damage equal to your crit stat.
Sample Talent: Cinderstorm
A spell on an 8-sec cooldown that launches 6 cinders in an arc that deal a bit of fire damage to everything they hit - presumably to be used for AoE situations.
The biggest change is that Frozen Orb is kind of taking the place of Frostfire Bolt. This makes me a bit sad, but it means that the Orb will now be a core rotational ability. Brain Freeze now resets the cooldown on Frozen Orb.
Beyond that, it seems to work largely the same way.
Sample Talent: Glacial Spike
This is a massive spell that requires 5 Icicles to cast, merging them with its own damage and freezing the target in place. With this talent, Ice Lance will no longer launch Icicles.
Mages are not getting much in the way of change, which is fine, as the class was in a good place in Warlords. Personally, I'm sad to be losing Frostfire Bolt, given that the spell always had this kind of cool "how does that work? Magic!" feel to it. I actually wish that Frost and Fire could borrow a little of each others' element on occasion, as otherwise only Arcane Mages feel like the true wizard-savant types. Still, I don't think it'll be too hard to adjust to any of these changes. I know some will be sad to see Combustion simplified so much, but oh well.
Next up: Paladins