The major limiting factor for Arcane Mages has lately been mana conservation. Everything Arcane Mages do costs a metric ton of mana, and unless we stack spirit, we simply don't get it back very quickly. Little known fact: each time an Arcane Mage passes gas, he farts out half of his mana pool.
Post-patch, a properly talented Arcane Mage now has a two-minute cooldown on Evocation. This essentially means that every two minutes, we can recover 60% of our mana pool at the cost of being unable to DPS for 8 seconds. There are two ways to view this. One: we can cast the spell every time it's up, allowing us to burn through our mana with wild abandon, keeping our DPS extremely high for two minutes at a time at the expense of dropping to absolute zero for a full 8 seconds each interval. It allows for a very aggressive spell rotation, one that burns all of your mana each cycle, but heaven help you if you get silenced or interrupted during one of your Evocations.
The other school of thought here is the more conservative one: Save your Evocation as much as humanly possible, using it only during advantageous times, when the negative impact is minimized, such as between boss phases or when fully hasted (i.e. when Bloodlust is up). This requires more active reigning-in of your DPS, a more conservative spell rotation, and is more suited to longer boss encounters, but ultimately results in more stable DPS output. Using this approach, the shorter Evocation cooldown granted by the patch doesn't really help in any measurable fashion.
I personally prefer the more aggressive method, mostly because I'm crazy like that. With the relative shortness of many of the current end-game encounters, I only tend to have to Evocate once or twice anyway, and the downtime obviously doesn't have as large an impact on overall DPS in shorter fights. It is also entirely possible to mix the two approaches, staying conservative at the start of the fight and when appropriate throughout, but switching to the aggressive, burn-down method when it's time to blow something up good. The shorter Evocation cooldown makes this possible. Overall, this is a very good, very welcome change for the raiding Arcane Mage.
Spell rotation-wise, though there are variations, I tend to go with something like this: Arcane Blast x 3-->Arcane Missiles-->Arcane Barrage. I tend to cast Arcane Missiles regardless of whether or not Missile Barrage has procced, but there are those who will forgo it in those situations where the proc didn't pop up. I try to time the following Arcane Barrage so that it leaves my fingertips at approximately the same time as the fifth Arcane Missile so that it also potentially benefits from the Arcane Blast damage increase (latency permitting), then I go right back to Arcane Blasting. I macro Arcane Power, Presence of Mind and my spellpower trinket to Arcane Blast, and use it to start off the rotation whenever it's up. A more mana-conservative rotation involves alternating Arcane Blast and Arcane Barrage, substituting Arcane Missiles in whenever Missile Barrage procs, but I find the DPS on this to be somewhat less than ideal.
My current PvE talent build of choice is the following:
This gets the job done on single targets, taking everything that maximizes DPS in the Arcane tree and nabbing Precision and Icy Veins out of the Frost tree.
PvP-wise, the Arcane tree is a whole different animal. In most cases, mana conservation is a moot point for Arcane Mages in PvP. We're still as squishy as ever, so the fight will be over, win or lose, long before we ever run out of mana. Thus, the stacking mana debuff of Arcane Blast isn't much of a concern. If we can manage to stay out of the line of fire (usually accomplished by some well-timed Invisibility and finding some cover) long enough to get a few Arcane Blasts off, we can pump out a very impressive Arcane Barrage or Missiles, and hopefully vaporize the poor sap unlucky enough to be caught in our crosshairs.
Our primary spell in PvP is still Arcane Barrage, which allows us to stay mobile and still apply consistent damage. Presence of Mind provides a nice extra burst, especially post-patch, allowing for Arcane Blasting even in situations where you don't have 2.5 seconds to stand around casting it. We still have crippling control options in the form of Polymorph and Slow, and our defensive repertoire remains formidable (Ice Block, instant Invisibility, Improved Blink, Magic Absorption, etc.).
The change to Evocation only makes us more dangerous. With Glyph of Evocation (a must for PvP)--if we can manage to get out of enemy range for a few seconds--we can regain our health and mana in large chunks. This vastly strengthens our largest weakness: low survivability.
There are a couple of builds I like for PvP, one that stays primarily in the Arcane tree, and one that dives a little deeper into the Fire tree to pick up Pyroblast.
PoM-Arcane Blast 58/13/0
Both of these builds focus on massive and swift burst damage, and still provide a lot of utility. There's a reason that Arcane Mages are possibly the single most whined-about class in PvP right now.
I say let's go out and give them something to whine about.
Every week Arcane Brilliance teleports you inside the wonderful world of Mages and then hurls a Fireball in your face. Check out our recent guide to gearing your Mage for Naxxramas, or our look at the goodies Arcane Mages are getting in patch 3.0.8. Until next week, keep the Mage-train a-rollin'.