I was reading that this year has been the best years for 6 and 7 in ages.
Australia's top order has got some stick but really where we are a lot worse than other countries is the middle order. 5,6 and 7 in particular. Voges averages sub 30 against anyone but the West Indies or New Zealand, Mitch Marsh is statistically the worst batsman in the top 6 in the world right now and nevill does try hard but he is pretty easy to tie down.
Like as a comparison Englands 5,6, 7 from the most recent test match for 2016
Ali 815 runs @ 50 with 3 centuries
Stokes 786 runs @ 60 with 2 centuries
Bairstow 1217 runs @ 64 with 3 centuries (leading run scorer for the calendar year at the moment)
Like Iafeta mentions Watling well he is on par with Warner this year for runs.
We have one batsman averaging over 40 for the calendar year in Smith (620 runs at 57)
The difference between Australia and the RSA can really be summed up by their middle order having some starch in it. They were 4/f**k all at Perth and dragged themselves to 250. We were 1/150 and collapsed to 250.
At Tasmania we did collapse a lot more embarrassingly but they had their wobbles but
Bavuma dug in (averaging nearly 60 for the year at 6) which allowed the innings to rebuild and QDK (averaging 80 from 7 in 2016) could counter attack. We had Smith watching in horror as the middle order said nah this is too hard.