Don't think there's been that much of a change. I feels like there's been a dearth of political talent of late. I feel that Hawke, Keating and Howard were much better leaders than the current lot (or maybe I was just younger and stupider).
Aussie has always had some fairly nasty parts to its society, but many parts that live up to the young, lucky country moniker. I think Aussie has always a been a bit tougher and rougher than NZ, less forgiving. I have a theory it's the climate.
I certainly think the Conservative movement spin-doctors Crosby Textor certainly have tapped into a nasty vein in NZ, Aussie and Britain (and perhaps Canada?), but it has to be there to be tapped into, or else it doesn't work right?
Also when a group is in power other groups tend not to stick their neck out, as mostly the only thing that happens is it getting chopped off. With Abbott, his guys feel empowered.