I have to agree with Kitru on almost every one of her points, though, honestly, in greater context I find 'low'/'moderate'/'high' short easy enough to imagine intended uses of, though numbers would be nice. Keep in mind that potency is great in the sense that it's already relative. Just also keep in mind the build-up and intended dynamics of the class to know the highest you should bring those potency values to (most roughly speaking: like PGL, or like LCR?).

This is also just a personal preference, but I'd really prefer to see abilities less hinged around near-purely magic attacks. Let the magic play off them, but you needn't make a fencer an elementalist. Abilities with multiple elemental connotations each would also work fine--Alight (Fire, Lightning), Glide (Wind, Water/Fire), Percussion (Earth, Lightning), Moulinet/Whirl (Wind/whatever), etc.--each with unique effects that lend themselves to strategies that can play into the elements eventually.