I don’t think the issue was defence for Australia today. They actually had a lot of gains but they had breaks, not wholly within and some other soft turnovers at least 4 times when they turned it over.
I also think Australia hasn’t adjusted to the umpiring style at all throughout this series, something that you could see they had worked very hard on going into the WC.
Overall though, NZ have clicked, Aus are probably a bit stale after a long run of success and have a bit of work to do to turn this around before CWG and WC.