Passing yards is an irrelevant stat just as 300 yard games are.
It's TD/INT ratio and YPA that matter.
Allen is playing great. They are winning throwing the ball. I am one who believes they can win even in the cold with that type of offense. If the Bills had a better run game and had 50 yards more rushing a game sure I would take it. Balance is fine. But there is no reason to try to achieve balance just for balance sake. The four best players on offense are Allen, Diggs, Beasley, and Brown. Play to your strength.