In what situation will you select cursed canting chains as your ex? In a world where design has moved towards debuff resistance and you're in a situation in which you've chosen to use your soul for damage reduction purposes, you'd use Joan. Then you'd probably take the 100% damage cut on a 6 turn cooldown ex skill. Or, if you prefer a defense buff lasting multiple turns at once (ie you're still thinking of cursed canting chains for whatever reason), you take the ex skill that's a presumably-small stacking def buff on a 2 turn cooldown that lasts 30 turns.