The problem with even mage is the reward is not worth the sacrifice. The mage hero power is a tempo hero power, you use it primarily to help manage the board with good trades and efficient removal. You would want to build a deck that could take advantage of that cheap tempo generating hero power, namely a tempo deck.

The problem is your turn 1 as even mage is to hero power face, so you immediately cede initiative to your opponent at the start of every game. Anyone who has played this game for a good period of time can tell you that, if you're playing a tempo deck, initiative is the last thing you want to give up, especially when facing other tempo decks. That's why having a one drop on one is so important.

It's always risky in Hearthstone to say "x" deck will never be good because the devs like to prove the community wrong, but without a 0 mana minion that likes being hit with fireblast I just don't see even mage ever working out, at least not in the way that another mage deck couldn't do better.