It's Probably Bruce with the Fear toxin in use. Red Hood is doing his own stuff like the Pre-order crapfest dlc showed. Tim is getting married and i doubt he's using the toxin. Oracle/batgirl obviously isn't Nightwing is taking care of Bludhäven I doubt is Azrael since after the side quest he is on the hunt for the order for what they did to him, the ending is open to theories so it might be him. Damian Wayne doesn't exist in the Arkham universe (as far as we know)