All I know is long range archery is non existent. I sat there and tested it for hours trying to hit things overlooking a cliff. The arrows either didnt hit, or went through the target or something, because they never caused any damage. And that's with 100 in Archery and all of the perks except for the second 'slow time' perk. Tried it with the mod that illuminates arrows, so I saw where they were actually going, and they seemed to just disappear.
Go to My Documents > My Games > Skyrim and open the Skyrim.ini file. Add these two lines to the bottom:
[Actor]
fVisibleNavmeshMoveDist=12288.0000
This makes your arrows hit pretty much anything you can see, if you aim properly. Without it the game doesn't register arrow hits at large ranges. You will have to aim a pretty good distance above your target to hit stuff you can barely see. Practice on mammoths.