HUD won't help you as far as flare guidance without an ILS. What it will do is enable head free + track/path/speed monitoring
Don't need flare guidance when you are visual.
In order to descend below minima I believe a Pan call should have been the minimum required in order to tick the "emergency" box.
In response to the thread about monitoring dewpoint etc. In 20 years of flying I have never seen a crew not take the trend of an airport into consideration and constantly monitor it if it is deteriorating. Years of flogging up to Europe with payload limited aircraft instils this in most crew members early in their career.
Lots of big swinging d***ks in this discussion and a few attached to heads. At the end of the day both crew delivered their passengers to their destination albeit a little late.
Given the less than adequate support provided by others who could have relayed the deteriorating weather information sooner I think they both in hindsight would have autolanded at ADL given the choice. The legal requirements necessitated a diversion and that's what both of them did. Mildura going to fog was not indicated anywhere until late in the piece and they were once again let down by others.
To the credit of both crews they flew their aeroplanes and focused on the operation at what must have been a very stressful time. No one died. No one got hurt. What would you have them do?