Sorry for off-topic, but what's the point of a rainbow attack if a decent portion of your attack is not coming from ranged attackers?

I can understand that causing the enemy units to stop at every possible opportunity (i.e. using a rainbow attack) allows ranged attackers more rounds to inflict damage. What, then, is the point of a rainbow attack if warriors are the main (or in the OP's case, the only significant) attacking force?