Like everyone else, I find jav cav utterly ineffective against heavy cav. Indeed, precious little beat heavy cav.

Jav cav are devastating against infantry esp. AI controlled as you can jog them around the map to get them exhausted and also attrit with javs so that there is an instarout upon charge.

However, this tactic doesn't work against heavy cav which are really quite fast relative to light cav. This makes for frequent instances of getting pinned upon a map edge or corner and slaughtered. Besides, any smart human opponent would ignore the negligible blows from the javs which don't do much against heavy cav and crush all your melee units.

Then, the archers would open up and strategic pincer moves made to pin and slaughter the light cav.

Your best bet for cost effective anti cav is to have a line of medium heavy infantry. Behind, position medium cav. counter charge the enemy cav in time so that the cav lock into melee right near where your infantry is. Then swarm their cav with infantry. You can use medium cav as youa re relying on your infantry to actually win the melee. This is better than a pure infantry line since cav is better at absorbing cav charges.