Expected goals is probably a better comparison of how clinical the strikers are. Auba scores as much as he is expected to over the course of his career as a striker, nothing less nothing more.
The better strikers, those that can create goals out of nothing scores much more than expected, but other than that serial bottlers like Cavani and Lewandowski is pretty normal as well, doesn't score much more than expected in terms of quality of chances.
This year probably because of all the sitters missed, but got back from some long range strikes he is still the only underperforming top striker.