After doing many SYD-CBR I think the time would be more like;
1. 30 min drive to the airport
2. 10 -15 mins to find a car park and walk to check-in.
3. 60 min to check-in, though screening and get to the gate
4. 45 - 60 mins block time (with only 30- 40 mins in the air)
5. 10-15 mins to get off the aircraft and collect bag
6. 5 mins to find a taxi/ hire car
7 15 minds to drive into the city.
Total time: 2hrs 54 mins - 3hrs 18 mins
And this would be on a good day!
High speed train is the way to go if we had one