This is a topic which has been argued ad nauseam on these boards, and you'll usually find many different responses. My personal take on it is that no change is required. I don't think the damage output is that much greater to justify changing the spell, and if you have multiple archers using the arrows, they're used up much faster. Also, remember that GMW on a bow does not help against damage reduction, so that would be a potential problem (unless you house rule that away too).