Weight Reduction and subsequent Bow Haste do not take effect until Late Velious.
http://www.tski.co.jp/baldio/patch/20010508.html
Quivers now reduce the delay time on bows, the better the quiver the faster your bow. We will not be listing the speed increase a quiver will give your bow, but you can tell the good quivers by their ability to reduce the weight of your arrows (better-made or magical quivers have this property).