The Master waited until he was just shy of being dragged into the basement anyway before just stopping his stuggle, abruptly enough that were it physical, his opponents would stumble, rolling as the floor crashed through into the basement, firing as he got a clear shot at Jack. Take him out first, and then worry about the others.
He ducked behind the debris from his arrival, already mentally marking Romana as his next target. Take out the one who wouldn't stay down, then take out the one he could predict the least. Then worry about his alternate and the two Doctors.