You need to break his horns before you can damage him (elementally at least) once his horns were broke I was doing 250 on Tornado, which is still shockingly craptastic but hey ho, SE seem to always screw mages over.
That being said they are supposedly redoing mage classes when they upgrade to the job system, we can only hope they make black mage worthwhile.
Don't give me that bullshit, this is the kind of idiotic thinking that resticts classes to playing one role.
Why even bother giving CON elemental spells if all we are supposed to do is heal, healing is for pussies.