I imagine Ning himself could have easily taken care of all the enemies, but he can't do it, lest he would reveal his darkness powers. That's a huge disadvantage for him when he's not working alone. I wonder if his closest allies, like Yue, would even care. Yue is basically whatever would be the Chinese analogue to Yamato Nadeshiko, so she would probably never doubt Ning and would instead be all the happier knowing his real power.