Ref the third or fourth crew members in the flight deck - is it a safer operation to have a the extra crew members in the flight deck? If the answer is yes then it must be less safe to operate with the standard two pilots and if airlines are concerned about flight safety then surely they would operate with three pilots - as it is safer?? Hell if three pilots makes it safer then 4 pilots makes it still safer!!
Modern airliners are two pilot operations - not three or four - the extra crew members are there to extend duty time.
With out having trawled through all the pages I wonder what mode they where in on final descent - if they where high and they where in FLCH mode - the Auto thrust would be in HLD . From what I can remember about this mode is that as the speed goes below the selected speed the A/T remains in Hld and will allow the speed to decay.