that would suggest that God and/or Jesus is subordinate to the Devil.
I think the idea in general has something to do with balance. In Shakespeare's tragedies, the world of the tragedy is said to be out of joint, unbalanced, and in order to get the equilibrium back, somebody has to pay, and so the tragic machinery proceeds along its inexorable course. Same thing here. In order to get the world back into equilibrium, somebody must pay the debt by way of suffering.