Fireborn would not be useless. You could still res to help your teammates while they are still alive. Most people orb-camp once they kill one person, so you are going to play man down anyway. Fireborn would allow you to coordinate with your team and pop it as your teammates flank. If everyone is watching your orb, wait until they turn their backs to cover the flank and pinch. Also, I don't know why you are assuming it's 3v1 when the lock dies and pops res. It could just as easily be 1v1 when the lock dies.