I have recently been forced to deploy javelins versus light horse archers (in conjunction with actual archers, natch) & found a variation of Caravel's spearman/jav-man tactics works rather well. Especially if you have hordes of junk javelin men "given" to you via a crusade -- they eat the arrows destined for your good troops, keep the horsies occupied, & if you can sneak into position let loose a volley or two occasionally to decimate those pesky Turkomani! & if they run -- who cares! They're javelin-men!