ask23, while "utter madness" might be a bit harsh,
willadvise is pretty much bang on otherwise. 8.05 will be the time the plane touches down (if you're lucky), not when you get off the plane. By the time you taxi to the gate, file off the plane, run through the terminal to the cab rank, you'll be lucky if it's earlier than 8.25. I'm in Melbourne on the course at the moment and I fly home a bit, and I tell my wife to show up 20 minutes after the arrival time, as that's usually when I'm standing out the front ready, and that's at 10, 11 at night even.
Having said that, if you persist with that particular flight, it'd be lucky to be a 5-10 minute cab ride. It's not far, just by the time they weave their way through all the morning traffic at the airport, and get to ASA, you're gonna be late no matter which way you slice it
As you said, we don't know your circumstances, but we do know the testing. I would in the strongest way suggest getting there the day before if you can to give it your best shot.