Hawkeye and Lady Shiva is not supernatural but would be over level 10.They are not called supernatural, but in fact they are. People in comics and anime do things that are beyond the scope of reality. For example, a common idea in anime and mange is that a warrior can move so fast they create an after image. That is not reality, it is fantasy (aka supernatural - or at least how I am using supernatural in this context).
The issue is the rules don't allow for the size of bonuses and number of fighting styles and feats they would have.
It's a game limitations to make the game simple.