Over the last several seasons, Zephrys The Great has proven to be an immensely effective control card. That's why the Highlander format is still the best choice in Mage class.
Descent of Dragons adds several well-established legendaries, such as Zilliax and Siamat. Together, these cards make up a solid high-value Highlander deck.
If you find Highlander Mage has a bit too much mana, then consider using Luna's Pocket Galaxy and Frizz Kindleroost. Both cards make your minions cheaper.
There is also a copy of Puzzle Box of Yogg-Saron in this list. Cast it in the late game and watch how the entire match-up suddenly turn in your favor.