Is there anything preventing someone with Arcane Background from using two Powers in one turn, taking a -2 penalty to each cast attempt?
As an action, a character may use a single power by declaring the Power he's using, spending the desired number of Power Points, and making an arcane skill roll.
Given a character can generally take two or more actions in one turn, suffering a penalty to all dice rolls involved, I feel this lands in the same category. There's the restriction of one attack per weapon per turn, and the arcane character could conceivably be a single weapon. That removes the opportunity to use two attack powers in one turn.
What about buff powers? Could an arcane character with sufficient skill cast Deflection and Smite simultaneously, rolling Arcane-2 each time?