Not to make the fatigue aspect irrelevant, but as some has said, 20-30 years ago, there was maybe a widebody, that flew once a day across the Tasman.
And look how much ticket prices were and the volume of traffic. High ticket prices, low volumes of traffic.
Now that we have 3-4 flights a day from each port across the Tasman, with smaller narrowbody aircraft, we have greater frequency, more aircraft, and more importantly, more jobs.
I know that there are probably those with the single digit senority numbers that probably bemoan the fact that there are now vast narrowbody fleets plying the Tasman, stealing their flying. But the reality is, the demand is for greater frequencies of flights leaving when they want to leave, going direct to where they want to go, not one large aircraft flying once a day, unless it is with a very large discount, on the way to somewhere else.
The reality is, redeye Trans-Tasmans are, to be blunt, one of the reason we probably have jobs. Yes, it allows utilisation of a otherwise idle asset, which yes, I do agree is not the most ideal time to be flying. But there is a demand for it, whether it be due to the large discount flying at that time of night or simply because it was the most convient. Schedules are driven by commercial. Its up to technical and resource planning/rostering to make it happen safely.
The biggest problem IMHO is not the redeye duties themselves but it is how they are rostered and how suitable rest periods are NOT protected by some operators, after and before the redeye duty.