Okay, it seems like I was just unlucky the first time around, because Exor went down on my 5th try. Don't get me wrong, though. Exor IS really tough... and the reason I beat him is probably only because I spent 3 Rock Candies and a Fire Bomb on him. The eyes (atleast one of them) are easily destroyed with Super Jump, and as soon as Exor's protection is gone you can just hit him with Rock Candies for 300 dammage each (party must be Power Blast'ed). Aurora Beams + Corona can really screw you up, though.

Anyways... now I've finally reached the Factory. In other words, I'm close to the end of this challange.