The Gladius is fine until you get the Axis Blade, which is fine until you get the Lionheart. Lightning's not a heavy hitter, and she has to give up a lot to make her one. The Organix makes her 70% slower, and the Hauteclaire prevents her from staggering enemies.

The Axis Blade and Lionheart are pretty well balanced between strength and magic, which is good because most of her Ravager attacks are a combination of the two. In addition, the Axis Blade's synthesis ability basically gives her permanent Haste, combined with its normal ability and someone casting Haste on her makes her attack pretty much nonstop. Late in the game, though, the Lionheart makes a better ultimate weapon, because the Axis Blade loses its synthesis ability at the third tier, which is really its main draw.

If you want to switch to a more balanced weapon now, you could always go with the Blazefire Sword. It's the default weapon, but it's really balanced and not a bad choice if you're looking at magic. Lightning uses physical attacks too much for the Edge Carbine to be worth it. But the cost of using weapons with higher stats is way too high to get any real use out of them.