I don't understand the change in the Master's characterization. This is a character, who according to the Fourth Doctor, would pull the wings off a fly before it was executed.
According to "The Deadly Assassin", an electrical scan of a Time Lord's brain pattern is made when they are near death. The Time Lord is in physical contact with the Amplified Panatropic Computations control, which does the scanning and transmits the data to the matrix.
So, how did the Master get the brain patterns of humans when the ones we saw die weren't in physical contact with the equipment needed for the scanning?