As a choice I think it's the right one - the RAN need long range and endurance - not something you get with a diesel.
The big problem is building the damn things - the UK has been building them since the '50's and still has problems - "Audacious" spent 4 years working up due to "emergent technical issues" in a class that is over 4 years old.
There are some nice people in Port Adelaide but the yard has had issues before completing high tech warships
Would the US sell them direct?