HI
I am sitting with the same problem. Our CO was appointed on 28/06 they requested more documents which was provided by 01/07. I enquired yesterday from IMMI as to how long they think we will still be waiting and they said hopefully they assign us to a new CO within the next four weeks.
They changed the system. If a CO viewed your file and they requested more docs, your application is not going back to the same CO, you get assigned a new CO after 28 days of requested docs.