I agree with this, I wouldn't undo the trade because getting out of Petry, Rutta and Granlund is still worth it IMO. I'm just saying that Karlsson's issues make him a piece teams cannot win with at his salary, so while the deal was worth it, it just replaced one issue with a lesser issue.
He is a "shitty team" player: you play him on inflated minutes on bad teams and he puts up a bunch of points, but once you play him on a good team (or even a mediocre team trying to be good), you immediately realize why he's not worth it. It's the same exact situation as Granlund, who has 56 points in 66 games for the Sharks this year.