We really needed our two experienced batsmen in Shaun Marsh and Ussie to stand up in this series and lead our batting in the absence of Smith in particular. However, Marsh has just 129 runs at 26 (which is admittedly a vast improvement on his last series), while Khawaja has 134 at 27. The next most experienced player, Finch (who Warne wanted as Test captain), is currently averaging under 20 which would seem to be about right for him based off his history.
Harris and Head, the least experienced, are probably marginal passes at this point if I am being fair, with averages in the mid 30s. If they had Smith averaging 60 and Warner averaging 45+, we would probably be talking positively about Harris and Head. But with the rest of the order failing, they all look pretty poor.