Reducing numbers from 11-7 (as well as reducing ability for ships to be present) also halves the Australian industrial contribution, that pushes up the cost per unit and helps creates subsequent valleys of death. Hobart might (or might not) have been the wrong ship but the big mistake was acquiring 3 and not 4 (or 5 or 6) — we now see ANZACs retire without replacement and Hobarts will be out of the water and the loss of skills in Osborne contribute to Hunter being still 10 years off.
I do tend to think that the
Hobart-class DDG design was the wrong choice for Australia, and that it was selected for the wrong reasons. Compounding that was the in the end, the options for a fourth vehicle were allowed to expire rather than have an additional vessel built. However, even had a fourth destroyer been ordered there would still have been a 'valley of death' simply because of the amount of time between orders placed for RAN warships.
Mention of the OCV's which ended up becoming SEA 1180 and the
Arafura-class OPV's goes back to the 2009 DWP, but it was not until 2017 that the designers were selected. Similarly, SEA 5000 which became the
Hunter-class FFG also had it's genesis in the 2009 DWP, but what ended up becoming the new frigate was not selected until 2018. This means there was a gap of about a decade where no major warships were ordered for the RAN, from 2007 when the
Hobart-class DDG's were ordered until the first of the
Arafura-class OPV's (and these are not really even proper warships). Had the
Hobart-class build been sized at six vessels like a 1992 review recommended for air defence vessels, that might have provided sufficient work to stave off a shipbuilding 'valley of death' since the yard and workforce would stay active. Unfortunately though, the order was only planned around building three or four vessels and even with the delays (planned and unplanned) there was a gap in ship construction. Given that there were five different PM's and six gov'ts in that period of time, that does not speak well for Australian gov't given the lack of orders placed. I do not really fault the Rudd gov'ts, in part because of how short the 2nd one was, but also because of some of the ideas kicked off by the 2009 DWP in the first Rudd gov't.
Given that the continuous build programme was not looked at by the RAND corp on behalf of the Abbot gov't until ~2015 IIRC, it would not really have been possible for the
Hobart-class destroyers ordered in 2007 to be a part of that, since that was not supposed to start until ~2020 when the destroyer build was supposed to already be in service.