I dont know what youre asking here.

I use gamepad, and what youre trying to describe seems like youre trying to melee an enemy as a black mage?

On gamepad, and i assume keyboard and mouse also when you select an enemy and then choose to attack it your character by default will face the enemy (unless of course you have this function turned off in which case turn it back on.)

Also if youre having an issue where enemies are getting behind you as a black mage youre standing too close to the enemy, stand a bit further back and never stand behind the tank. Black mages have a quite extensive range so try to get used to standing further?