Frost mages, apparently:
http://www.mmo-champion.com/class-mage/frost-pve-faq/
Didn't even know that Frost was a viable PvE spec, but I guess by timing the right CDs, it works. Spamming Frostbolt couldn't make DPS any easier... well, unless Blizzard decides to give classes an ability that passively does DPS that scales with GearScore. >_>