You haven't leveled a single monster?!? Wow... I love the depth of the leveling system, like you say, its rather detailed but thats what makes it so great, and personally I only level my mobs up with potent items (unless its for something like a sent then I don't mind using HP items).

I am entering the final chapter of the game and I am still finding myself using the Albino Lobo (though my blue chocobo is level 60 and will soon surpass him) that's one of the things I love about the levelling system for the monsters, the fact that they don't use CP but items instead makes it more convenient to level new monsters (I am just about to go after the Tonberry and have been hoarding my mats so I can pump his levels up somewhat substantially).