well in arena they meant to do that, they wanted to make sure you couldn't just back-peddle and fill them with arrows
That has already been taken care of, backwards running is much slower than forward.
I hope NPCs are fast, but not faster than the wild-life, the arena NPCs surely ran faster than any wolf, deer, boar, bear, mudcrab, minotaur or horse in whole of Oblivion. That's just wrong.