DD must include crime and perceptions of crime. It must also go further than this to understand trends including areas that may be tending towards slumming down vs those areas that are gentrifying.
Well Im a bit biased but Illawarra/South Coast is one. Central coast and north to Newcastle is another. It really depends on how far from the city you can tolerate, what your goals are etc.
Personally from that list a basic little house out the back of southport would be my pick. Not many under 400 but a few.
There are other good markets sub 400k closer to sydney if you want that kind of thing too.