I was just reading this again the other day. The dead man in the life raft discovered some months later is very interesting. It seems unusual that a ship with some 725 men (the number I remember was about 600) could sink without a single survivor. The German surface raiders were very successful in the early part of the war, especially considering they were just armed merchant ships.
725 includes the number who died from the Kormoran as well - 645 on Sydney, 80 on Kormoran.