As I said it before a barbarians critical POWER comes from a 19-20.
Take a paladin and barbarian using an ESOS. Yes a barb using an ESOS will obviously have a threat range given the ESOS but there main power from crits are on a 19-20. Then take the paladin using ESOS. Paladin casts Holy Sword. Now that ESOS is a x4 on every crit and the crit range is higher. Now Zeal which 10% double strike.