The only AU I like is the LWB cars and the T series - you're on point about that
IRS setup, I think it was a massive step backwards going to the control blade style on the B series/FG compared to the double wishbone setup the AU cars have. The Holden setup in my Caprice is a joke, you can crack/break the K frame without even abusing it - they **** the bed with normal driving/use.
The biggest eye opener to me was when I drove a customers AUII Fairlane Ghia across their bumpy paddock, expecting to need go to bras n things for a sports bra fitting prior to driving it off road, I hit all the bumps and it barely upset the car and I smoothly floated over the paddock - it drove about on point with how my E38 7 series did with a very fancy self leveling hydraulic rear suspension setup.