My understanding is that the Navy brass have long considered the IPVs to be too limited in capability to do much useful work, but still requiring half the crew of an OPV. It remains to be seen whether the deployments to Fiji will affect that view. The decision to pull the IPVs out of their de-facto mothballed state is presumably due to the absence of other vessels; with three vessels retired in the fairly recent past and one frigate in refit. The Plan makes it clear they are intended to be gone by 2025.
I agree with your wider point that the navy still has too few vessels for the range of tasks they aim to undertake, and zone of ocean they are supposed to cover.
Really? From what is widely available from the net and from Navies own admission is that they purely did not have the resources to crew them ie specialist positions such as marine engineers in particular due to recruitment, replacement and especially retention issues (due to higher paying civilian jobs) and only snowballed during the civilanisation debacle so had to come out.
Customs and MPI worries from the same period confirm they also could not meet their patrolling targets (along with navy, both IPV and OPV) for the same reasons, lack of resources, so surely if crewing was not the root problem then one would obviously cancel out the other as in IPVs would have been used and patrols would have been done.
Every ship in the navy has the exact same core crew requirements ie captain, OOW, engineers, medic, seaman etc irrespective of size or role it's only the basic number of which adjusts accordingly so obviously the larger fleet units with the "glamour" status'es and role dependant get priority for crewing and seemingly rightly so as imagine the uproar if say an ANZAC was mothballed due to lack of key crew? Would also not bode well for justifying their replacement. Average joe just assumes everyone in the navy drives the boat just like everyone in the airforce is a pilot and has no clue about specialist roles required to make the wheel spin.
I'm sure if navy could afford (littorally in some instances) to keep them then they would but it's a hard juggling act when you cannot put to sea 1 ship nevermind 4 as the pacific patrols have proven they can actually deploy and patrol (as in do their job) despite how certain politicians try to spin the situation to save face in the eyes of joe public taxpayer for yet another seemingly bad defence investment.
Under resourced is not the same as under required, just depends on what costs the least to justify that'll win the argument. IMO we should be funding and resourcing the 3rd frigate, 3rd OPV and retaining the IPVs (they also have other tasks) if govt was actually serious about our international, regional and local responsibilities as a small navy getting smaller only makes things harder but alas even our mighty navy is at breaking point and somethings gotta give in that large ocean so it's a classic case of which capability can we talk our way out of with least resistance from an apathetic public, reminds me of the ACF axe in some ways. Govt sits pretty each term meanwhile DF shrinks just that little bit more in terms of size, capability and outputs each decade.