Just to make sure, you're not confusing a fencing foil with a rapier, right? With fencing foils being the wobbly things they use in fencing matches, and rapiers the long stabbing swords.
Looking at the image, the weapon seems fine. Narrow taper, good for stabbing. As thin as a rapier should be, but could be a bit longer. One thing I do have to criticize is the guard though - more specifically, the guard on the inside. Might stab into the wrist, so that's bad. Apart from that, I'd guess the balance to be about at the end of the blade, so it's easy to move the tip around with tiny wrist movements.
Though looking again... the black part of the guard irks me a bit - but I can't say too much about that cuz I don't have a lot of experience fencing with rapiers. For a fantasy weapon, it has a decent design.