"Bingley stood rooted to the floor, frozen with indecision, his gaze ricocheting from Darcy to Parrish to the women. Elizabeth didn't understand his hesitation. How could he possibly believe Parrish's claim? Could he not see that Elizabeth was bound to the chair?"

Our compliant Bingley could not be this wrong! Indecisive about who is in the wrong; restraining Randolph. Of course, until recently even the Darcys thought that Randolph was the guilty party.

Also, Caroline is bleeding from her self-inflicted wound, but is able to restrain Elizabeth.

Are these actions a tad unrealistic?

The fight scene between Parrish and Darcy is reminiscent of the climax of many movies and TV shows. In fact, I can easily see this book dramatized.