The new 51 point talent in the Arcane tree, Arcane Barrage is simply awe-inspiring. The spell description...
18% of base mana
30 yd range
3 sec cooldown
Launches several missiles at the enemy target, causing 936 to 1144 Arcane damage.
...simply doesn't do justice to the practical impact of the spell . This is essentially a short-cooldown instant cast nuke with a high damage coefficient and base damage higher than a max-rank Fireball, all for a reasonable mana cost. To put it more simply: low-mana, high-damage, instant cast. Even simpler than that: win.
In PvP, this spell will be an Arcane Mage's most commonly used spell. You'll smack your opponent with it every time the cooldown is up, and use the 3 second wait to cast other instants like Fire Blast, a PoM-Pyroblast, Slow, Blink, Frost Nova, or something similar. You will be able to make very good use of the spell in Arena, alternating between sheeping your focus target and nuking your kill target with this and other instant casts.
In raid encounters, an Arcane Mage can look at this spell as a 3 second nuke, only one which you cast and then have a couple seconds in-between to cast other things. It should fit into several different rotations, including my personal favorite:
Spam Arcane Blast until Missile Barrage (more about this beauty in the Arcane Brilliance column later today) procs, allowing it to fit nicely into the cooldown between Arcane Barrages. Once it procs, cast Arcane Barrage, fit a nice 2.5 second Arcane Missiles into the gap, follow it with another Arcane Barrage, then back to spamming Arcane Blast. Wash, rinse, repeat. If Presence of Mind happens to be up when Missile Barrage procs, use it to start the round of instant cast spells, simply because with Arcane Potency each spell that doesn't consume PoM has an additional 30% chance to crit, and you'll be casting three spells in a row that take advantage of this buff before finally consuming PoM with a Pyroblast or other nuke of choice and resuming your Arcane Blast spam. That may have been the longest sentence ever. I don't know!
With no talents to reduce mana cost, Arcane Barrage will cost 403 mana at level 70, and 588 at level 80, so we aren't exactly breaking the bank with this spell. To put it in perspective, Fireball and Fire Blast will cost more mana, Frostbolt and Frostfire Bolt will cost slightly less, so the spell is about where it should be in terms of mana cost.
The thing I'm most excited about with this spell is that it is so flexible. There isn't a single aspect of the game in which this spell won't have its uses. What's not to like? I mean really, if you can think of something, let me know. Why shouldn't I love this spell?