Even if you value Rakell like his normal career self, this deal still sucks for the Penguins. It's a struggling former high draft pick and a bottom pair tough guy that would likely be in the coach's dog house. Xhekaj has value because NHL GMs grossly overrate toughness, but Dach isn't an attractive piece right now.
The value sucks for the Penguins because Dach and Xhekaj aren't appealing assets to the Penguins and the value sucks. You don't pull off a 25 goal, 55 point top-6 winger having a terrific year for that, especially with the team adding on top of the winger.
If we were valuing Rakell as the 40 goal, 70 point winger he was on pace for this year, this offer would get laughed out of the room by Penguins fans.