Paradox Interactive have recently confirmed that a duel mode has been added to Magicka: Wizard Wars as a direct response to fan feedback.
Magicka: Wizard Wars is currently available on Steam via the Early Access feature. This allows the developer to release an Alpha or Beta version of a game. This allows devs to receive feedback which can directly impact the development of the game. This is the case for Magicka: Wizard Wars with fans requesting an arena style 1 vs. 1 gamemode to play.