The truth of the matter Jason is that NZ has let it's Defence budget slip significantly over the years vis a vis Australia and other nations. Less money equals less bang. The IPV OPV MRV are possibly envisaged to have to shot at nothing more than the odd trawler in our fishing zone, they are armed as auxilaries, as is the Endeavour, which only has light arms. When the contracts for Project Protector were being tendered out, it was thought publicly that the NZ$500 million available would only be enough for the MRV and OPV, the Moa class were to be upgraded. There seems to have been a slight massaging of the budget, less bang but 4 more IPV hulls, the Moa with their 12 knots were never good enough to act as a deterent to a 20 knot trawler.
Part of the problem Jason, I feel, is the way the budget is broken down these days. Once the budget would have read "11 billion for health, $11 billion for education, $1 billion for defence and everyone was happy" Today it is read "an additional $50 million for 2000 more cataract operations, and additional $30 million for 500 more hip operations, an additional $7 million for low decile schools, an additional $4 billion over the next 10 years for defence" and people start complaining about health waiting lists, low benefit levels etc and how all the problems in their particular area could be solved with that obscene amount going on "toys for arm chair generals" We now have vocal Green MPs that make no secret of their desire to reduce defence to IPVs and OPVs only. It puts defence funding on the back foot, and politically unpopular,having to explain why money needs to be spent on guns instead of hip operations.
A lot of the new defence funding merely covers inflation, upgrading infrastructure that is long overdue, eg housing that is generally old and run down, bringing salaries up to the levels of those in the private sector, and bringing capabilties up to very limited standards so we can operate with others in peacekeeping.
Hopefully a case of "fitted for but not with" roll on the National government sheese. Still I suppose the thinking is the frigates handles any major confrontation, and the 25 mil keeps crew numbers and costs down.