in my current casse campaign i've used a rather simple trick to get around javelins...

i allow the enemy to come to me, and try to pair two of my units with javelins (any of the basic infantry units have them) against one of theirs. that means in the exchange of javelin flinging, the enemy unit will inevitably come off worse...then it's just a mopping up job. it doesn't avoid some javelin casualties, but it does whittle them down fairly swiftly.

that is to say, javelin the javelinners.