I don't seem to have an issue getting "1" sequence numbers. I believe it depends on what flights you take (eg *very* early morning vs other times), the types of planes (eg QantasLink Dash- 8 vs Qantas 747's ) , how you check in and whether the flight is deemed a connecting flight.
Today I had a 5am flight (yuck!). Checked in through quickcheck even before the checkin staff arived and while the airport was very quiet... so got sequence 1.
If you check in through Quick-Check, then you can also get the same day's return tickets ... so technically a 6pm or so flight could have issued tickets around 7 or 8am. (I think the limit is 10 hours, but not sure). Also, the checkin staff can issue you your return tickets within the same time frame if you're doing a same day return.
Also, it's possible to fly from say Darwin to Sydney (5 hrs or so), and pick up both boarding passes for Drw-Syd and Syd-Mel when checking in at Darwin... If the first flight is a red-eye leaving at midnight, then you've got no chance of beating the connecting pax.