You know, a lot of the espers have physical attributes that make it easy to assign them a zodiacal sign. Hashmal has the face of a lion, Belias has the horns of a ram, Adrammelech has the head of a goat, Mateus swims like a fish during his ultimate attack, Zeromus has the crabclaw, Ultima is the only chick, Zodiark looks like tiny snake, Zalera has a second head thanks to that shamaness, Famfrit has a buer of water (or darkness, whatever), Chaos has the head of a bull, Shemhazai has the body of a horse...

As for Exodus and Cuchulainn, well... the only way you'd know he bore the sign of libra was if someone told you. Cuchulainn you might be able to guess if you assumed he'd stabbed himself in the head with his own stinger.