Agree with Griff and Mira, nothing weird in his physical shape. It was not so fast. Also, remember that the sword levels the ground, so I am sure it helps to prevent some fatigue. But he is not better than Sanya, that is why he screws it in the end. As Harry said, he is new.
His weapon is a super weapon, totally overpowered, but he is well deserving of it and he proved with his faith not only in the Good but also in Harry (after a time of doubt). As I said in another place, I hope Ramirez do the same journey in future books.