Thanks for the details everybody.
Still looks like the PF is chasing the glidepath with his pitch corrections using the RA calls - so I conjecture that the switch to listening to RA was subconscious.
There seems to be no valid comments from anyone on the flights deck about pitch attitude or rate of descent, so I don't think these are being monitored.
The crucial bit is 08:40:42. I think the PF makes a small correction having heard "100" twice, and now thinks he's level. The further call of "100" 6 seconds later confirms this in his mind. In the stress of trying to find the runway, he's forgotten about the dip. These six seconds make the approach unrecoverable.
It's a credible scenario and explains the path of the aircraft. The detailed graphic #506 is really good at helping to recognise this, thanks janeczku.
Let's also bear in mind that whilst the PF may have originally known about the dip, did the General, or the Nav, who are the one's making the altitude calls?