If you are happy to sit at the very back (which will mean you are last off and may impact your immigration wait time), the 777s normally have two or three rows at the very back in 2-4-2 set up rather than 3-4-3. The banks of two on either side are slightly preferable in my opinion. I would avoid the very last row though in case the seats don't recline.

Transfer security in DXB is pretty good and coming from US you may not even have to pass through it so sitting at the back will only potentially delay you in Australia.

I suppose there is also the risk the meal selection may be more limited sitting right at the back.

On the plus side you are more likely to get a free seat next to you sitting right at the back.