Paladins do not have bonus against cavalry, they have 14+4 "normal" attack. The anti-cav armor means catas take less damage from halbs, camels, genoese crossbowmen, etc(units that have bonus against cataphracts).aoe2stats.net says Elite Cataphracts have +16 armor bonus against cavalry.
I don't think it's right, because then Paladins would do 1 damage to Cataphracts. Can you explain what aoe2stats.net means, or confirm that it's exactly what it says?