Icy Veins and the Raiding Mage

2.3.2 hit the World of Warcraft today, bringing several changes for mages. Mana gems have been buffed to have multiple charges, and the former staple of the frost tree, Ice Block, is now trainable for all mages, replaced by the talent Cold Snap, which has been moved down in the tree. Taking the place formerly occupied by Cold Snap is Icy Veins, a new frost talent much anticipated by the raiding mage community. How will Icy Veins affect raiding mages? Let's take a look.

The Basics
Icy Veins is an instant cast spell that lasts 20 seconds on a 3 minute cooldown, and is located 11 points into the frost tree. Its tooltip says that it "Decreases casting time of all spells by 20% and increases the chance your chilling effects will freeze the target by 10% for 20 seconds." The "decreases casting" part is a tad misleading; instead of directly reducing your cast time, IV increases your spell haste by 20%*.

What Spells Does Icy Veins Affect?
Icy Veins works on all three schools of magic that mages use. If you have the talent Frostbite, any frost spells you cast while IV is up will also gain the 10% bonus to freezing procs. If you don't have points in Frostbite, you'll only get the haste benefit (which is still nice on its own).

Will Icy Veins Stack With My Arcane Power/Heroism/Combustion/Quagmirran's Eye/Troll Bezerking/Mystical Skyfire Diamond/Bloodlust/Spellstrike proc/etc?
Yes. (Math-happy theorycrafters out there, please note stacked haste effect math gets a little tricky here.)

So Icy Veins is a Good Talent for All Mages?
Icy Veins has great potential for deep frost mages, PvP mages with points in frost already (that should be all of you, right?), and progression PvE mages who aren't hurting for mana and can afford to put 11 points into the frost tree. In PvE, your particular mileage may vary depending on your gear, group composition, the encounter in question, and your playstyle, but some of the initial number-crunching from the PTRs suggests that 10/48/3 fire mages who drop clearcasting to pick up Icy Veins will see their dps go up by ~2.5%.

A 2.5% DPS Increase! Wow!
I agree, but here's an important caveat: the only thing Icy Veins (and haste in general) does for a fire mage is let you burn through your mana bar faster. If you're OOM by the end of the fight anyway, this talent is virtually worthless to you.

Wait, Why Would Anyone Give Up Clearcasting? That's a Lot of Mana!
The general thought process is that the changes to mana gems in 2.3.2 should offset the loss of clearcasting procs. Plus, fire dps is pretty efficient these days anyway.

GMW, Tell Us! Are You Changing Your Spec Again?
I am indeed.

So, Tell Us How You're Speccing Firkin in 2.3.2.
With pleasure, my capital letter overusing friends. Here's my thought process.
Before 2.2, arcane was the name of the game. I switched back to the classic 10/47/3+1 build in 2.3, as it once again offered the best dps and mana efficiency for progression raiding (and vastly decreased my weekly mana potion budget).

In 2.3.2, I'm thinking the best raiding mage builds will be 0/47/11+3. I'll keep all the old fire talents from the classic build, along with 3/3 Elemental Precision. To that, I'm adding 5/5 Improved Frostbolt and 2/2 Improved Frost Nova to pick up Icy Veins in Cold Snap's old spot.

The three remaining points will be heavily debated on forums and blogs. The major options I see for them are:

• 2/2 Arcane Subtlety and _______ - The conservative choice, this lets you keep your 40% threat reduction in arcane for AE spamming on AOE packs.
• 3/5 Impact - For a Blackout-like stun effect. Fun in PvP, sometimes handy in PvE, but I won't be doing it because I date a tank, and he gets grouchy about random stun procs.
• 2/2 Blazing Speed and _______ - A talent I've wanted to play around with but never gotten around to, but the proc is probably a bit random to provide a significant benefit. On the other hand, there are a ton of endgame raiders walking around with [Boar's Speed] on their PvE boots, on the premise that every little increase helps in fights with lots of maneuvering.
• 3/3 Improved Frostbite - For the PvE/PvP player, there's a certain logic here. Icy Veins provides a direct boost to Frostbite's freezing effect, which is something that you almost never want to happen in the controlled environment of PvE raiding, but is great fun in PvP. But since a fire mage won't be casting frost spells in PvE (at least not 97% of the time, and 2% of the remainder will be on Frostbite-immune bosses), this combo lets you have your cake and eat it too.
• 3/3 Improved Flamestrike - I'm leaning towards this one. I'm not sure how dangerous skipping Arcane Subtlety will be on trash, but a 15% crit bonus on Flamestrike means that I could default to spamming that instead of AM if I need to.
• 3/3 Improved Blizzard - As with Imp Flamestrike, the idea is to come up with something to replace AE spam on AOE packs. Used correctly, Imp Blizzard is actually a really excellent utility tool for AOE pack control, but for a fire mage it won't compare in terms of damage.

I Have More Questions About Icy Veins! Where Can I Turn?
Lhivera posted this great Q&A on the talent on the official WoW boards. In addition, the Elitist Jerks forums are always a good source, but you may have to dig around a little (or a lot).

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*Math-happy theorycrafters should note that +20% spell haste is not the same as -20% cast time; it works out to more like -17% cast time.