effectiveness of horse archers RTW/BI

I played as the pathians in RTW, and loved the horse archer's ability to stand off and shoot, and skirmish effectively. Having tried a similar thing in BI as the sassenids, I find that my cavalry are slaughtered on a regular basis by roman infantry who chase (!) them and stick them full of javelins. Now, it is a while since I did athletics, but I watched the olympics and most people can't throw a javelin all that far (+-40m) - I do archery, and regularly shoot at around 80+m.

Has anyone else noticed this drop in effectiveness?

u can always modify them to become more realistic

Then just use your clibinarii as horse archers, with their 2(?) volleys of arrows. They should be harder for the Romans to take down, and then charge. Or, just get them to fire all their javelins at your general, who should be nearly invulnerable due to the power of the Clib Immortals. Then, start using your cheap cavalry: the horse archers.