Thanks for your input FCeng84. The difficulty with the '25k within two minutes' requirement is the congested airspace in many regions of the world. In the worst case scenario rapid descent before or without ATC authorisation could lead to collision, which would clearly be more hazardous than hypoxia amongst some pax. TCAS in RA mode might give inappropriate commands and in TA mode might not give sufficient data to avoid conflict at very high descent rates. Unless there has been a change in policy, the 757/767 QRH also requires restricting airspeed if airframe damage is suspected (my highlighting).
