Blizzard likes to give Mage free stuff like they did with secrets and Kirin Tor Mage. Now you can also cast elementals for free using the new Rastakhan spell -- Elemental Evocation. Cast it, play an elemental, and then cast Scorch that costs only one mana. This is currently the cheapest and the most powerful combo you can do in Elemental Mage.
Another great new card is Arcanosaur, a 6-mana elemental that deals three AoE damage. It has a condition to play elemental last turn, but in this type of deck that is practically guaranteed.
Lastly, Cauldron Elemental can make your other smaller elementals bigger and more dangerous for that final lethal attack.