1500' FPM sink? I doubt it's that high. Clean, 250KIAS idle descent is typically around 1300' FPM. Coming down the glide slope, at 180 KIAS (+/-), Flaps 5, is under 1000' FPM.
Granted, both examples are with idle power and no drag from damaged or windmilling engines, but IMO it's probably less than 1500' FPM.