Just my $.02 for now
While we have generalized fatigue, and this crew seemed to have had "adequate" rest, they may have actually just been really tired. On the other hand, their conversations may have been just shop talk.
Overall, it appears to me, that they had OK lateral situational awareness, but very poor vertical SA.
I've been trying to decipher just how high and fast they were at any of the fixes. If anyone has got that, please share.
If I had a 1,500 FPM sink rate going at less than 1,000 AGL, I would seriously consider going around, and definitely would have at the "sink rate" call that close in.
Regards,
OBD