The thing i don't like about this "suggestion", is because it will need to "relearn" the class all over again. Wich we already do everytime there was a patch change.
At the moment, with an horn bow, i already need to aim way higher than the target, wich leads to :"guessing where the target will move, guessing how long the arrow will fly before hitting the target".
I understand that you just don't want people sniping with hornbows (wich at the moment, only a few effectively do, mind you), but the reason i choose the hornbow over the longbow is for a different playstyle, wich is... fast aiming. I already find it easy enough to shoot down horses, and lowering missile speed will just INCREASE the damage i do to theses horses, wich will undoubtedly result in a damage nerf (ZOMG, my horse died in one hit ! I don't care if it was an headshot and i was galloping to him, no fair). So in the end, the horn bow will have less missile speed, and less base damage. Now tell me how that is not a nerf, but actually a buff.
And seriously, leaving the rusbow alone is... clearly not a good idea. You want to make bows different, then lower the speed rating of the rusbow wich is nearly as good as the hornbow, even though it's way easier to aim with it.
I personnaly think there's already enough difference between the bows that make people choose one over another.
Longbow : huge damage, slow reload speed. Used in ambush long range against non-moving targets, or in mid-range against melee.
Rusbow : Good damage. Good reload speed. Good accuracy. Best overall bow. imo
Hornbow : Decent damage. Good reload speed (slightly better than rusbow). Used against cavs, or archer duels. (not ambush mind you, what's the point of shooting one time if you know you need 3 arrows for that archer, and that he'll easily dodge thoses curved arrows you send him)
Tatar bow : Why would you use that if you're not an horse archer with 12 strength. Please enligthen me.
PS : If lowering missile speed is, in your way, considered as a buff, then please ask the devs to lower your bow to 8 missile speed = AWESOME HUGE BUFF. Or, just take a throwing weapon.