@spyfy is right. For AOR, trips to US should have no effect. Officers in Sydney are mindless robots pretty much just looking for unanswered questions, missing documents, signatures, dates etc.
I too am waiting for my AOR, application delivered on Oct 13th. Given average time to receive AOR is 30-35 days, I would give it till end of next week before i start panicking a little.
As for a theory on how it's being processed, I think every officer has a pre-assigned pile of applications which are randomly chosen from a bin. I'm assuming this bin has all applications delivered between Oct 12 - Oct 18/19 or maybe 20 ... a weeks worth of applications. Now some officers are processing fast, others slow. This explains the random order of AORs, and why only Oct12 -20 applicants have received it so far. I guess their plan is to finish these applications before moving on (I truly hope!).
I also believe they have a small % of officers working on C6 applications, while rest are still going through C24 apps. Slowly they will all transition over and things will speed up. I believe they did this because of the vast number of applications received after Oct 11. I would assume their goal should be to get to average AOR in 30-35 days by November 11th - 13th (roughly 1 month after C6 was implemented).
I also hope that all C6 applications will be sent to local processing center in
order of receipt (none of the C6 applicants have their statuses updated to "In Process" yet)
. As CIC's website indicates applications will be
processed as such. This last bit is too much to hope for though.