Well, if we consider the archer holds his bow + arrow with one hand when the arrow is nocked, then it's okay to be able to run... but, if that is the "nocked arrow" state, then the time for shooting should be increased over a "nocked arrow" state where the two hands are just ready to begin to draw, which is not the same as wielding the arrow + bow in one hand, and this second flavor of "nocked arrow" should decrease movement speed a little bit.
Although all this might seem completly reasonable and more realistic, I already see how it could turn out for balance. It would mean a great increase in the cheap child's game of going in and out covers at lightspeed, because it will become way easier to do for bad archers that don't have the timings right. I doubt it will ever be done, sadly this would require an awful amount of animation creation, and most of the few anims that were made by players are... sorry, utter crap. It seems the dev team concentrated on choosing the worst ones to add them in cRPG, with the goblin archery, the ultra jumpy insta-2hstab, the retarded 1h horseback stab, and the magic hafted blade horseback swing. Furthermore, it needs a counterpart to balance the little buff. Archery is more or less fine as it is.