Disagree about them being test quality although the jury is out on Hales, but I wholeheartedly agree with your second point, we need some grit and concentration, not more dashers.
We have Cook and Root to amass big, slower hundreds. We must give Bairstow a chance up the order, he's our 3rd best batter.
Hales and Buttler both have big hundreds in them, the pace of the scoring is largely irrelevant.
The problem we have is 2 of the top 3 are getting out for next to nothing. Neither are good enough and we don't have old school slower scorers in good form.
We've tried Jennings, Compton, Balance and Hamed. The first 3 aren't good enough and the other is out of form.