It’s not a one or the other issue.
We all know the batsmen are rubbish, no one is hiding from that.
It's not one or the other, but the batting is the root of the problems.
Imagine being a bowler in this side? Knowing that, on any half decent wicket, batsmen with a brain will just be patient and tire you out, get to even a middling score in the low 300s...then you'll have to come out and face fire after the top order fails, then after having to save the blushes of the bats, you're out there again, 135 runs behind already with the opposition not needing to take a single risk to stay in control.
That takes its' toll and it's happening just about every test. I'd bet quite a lot that if we could somehow get this side scoring 400s, those bowling averages would come down in kind.