I'm playing on PS3 so modding is impossible for me at the moment. I have fortify archery stacked up on my armor, plus a legendary daedric bow. With the five Archery perks + the stacked bonus + the legendary daedric bow. I'm doing roughly 500dmg a shot, I don't need the 3X dmg sneak attack perk.
Let's see...legendary daedric bow is ~90 damage with the archery perks 5/5? Enchants get that up ~200% if you have it on ring, gloves, necklace and helm, so 270-ish, plus arrow damage.
How are you getting 500 damage shots?
*will have to go mess around in Skyrim to check numbers*
Edit: I bet I'm not thinking of the bow's base damage at skill 100.