Nah man he is supposed to have been that young and he didn't overpower the vampire it easily overpowered him it was only through his masters death that distracted it enough for him to kill it. The first one he stabbed in the eyes with his blades which pretty much finished it the second one he actually turned into a full blown werewolf to kill. Even if it wasn't intentional. Plus him being this young could add an interesting aspect because I can only imagine what a bunch of veteran warriors would think of a young assassin.