Let's look at the lineups.
Now:
Rielly-Ceci
Muzzin-Barrie
Dermott-X
Then:
Rielly-Hainsey
Muzzin-Zaitsev
Gardiner-Dermott
I'm not as high on Barrie as many others, so I think him instead of Gardiner is a rather lateral move. Ceci replacing Zaitsev is a lateral move. What we are left with is some of our depth pieces instead of Hainsey. That's looking like a downgrade. So just based on talent, I think we moved laterally. Any improvement is probably not significant, so I'm kind of with you here. If we run with both Ceci and Harpur, we might actually be worse.
However, I think the on-ice impact might be improved. For one, we replaced our #3LD for a #1RD, which means a redistribution of ice time towards better d-men. We no longer have our three worst d-men sharing half the ice time, we can give a large portion of that to Barrie. That makes a difference. We're also taking a step towards being a much harder team to read on the breakout, which has been an achilles heel for us. That helps too.