My main use for javelin cavalry is harassing other troops and sometimes trying to lure away enemy cavalry. Of course in game effects don't really correctly represent the punch harassing could have had in real ancient life, but it still does the trick most of the time. Javelins shouldn't really be stronger, but I'm all in favour of the more accurate idea. Although that applies mostly to specific situations where the throwers are standing more or less still and can actually pick out an individual target. If they're just vollying away the impact of the javelins is fine as it is.