There is much merit in the above discussion, if only to increase our understanding of L/D ratios, and their implication. We must recognise, though, that the crew must have been hoping for, or even expecting, a sudden recovery in the thrust shortfall. Double (all) engine failure is one thing; slow and/or partial engine acceleration is another.
One of the most relevant data strings that we would-be diners have been starved of so far is the actual thrust from TOD (top of descent) to the point at which the engines noticeably failed to respond to the autothrust command. This missing information has been a major inhibitor to our discussion from day one.
To spell it out: could this have been the first call for thrust above idle? In which case, how long had the problem been lying dorrmant?