I agree wholeheartedly with your assessment in your second paragraph. If only there were a drill that could generate puck bounces/confidence, but alas...
As for your question on Werenski, funny, I had the same initial reaction. From my estimation, he shoots as much as any defenseman on the team. But then I dug into it a bit, and here's what I found: according to naturalstattrick, Jones/Savard have combined for 194 5v5 shots(119+75). Werenski has "only" 87 attempts, but nobody else really shoots the puck much from the left point. So my guess is that it looks bluer not because of Werenski but because of a lack of secondary shooting.
To be fair, Murray will be an RFA after the season, so the Jackets should be able to retain him going forward without much issue. But your point on Johnson is well taken. The only thing is, trading a defenseman away before a playoff push is a bit counter-intuitive, but who knows what he would return.