The biggest component of the blowup was Galch to wing, which you're completely ok with. At best, this is a very minor criticism.
Why? How are any of the reasons you gave for supporting that move this season not applicable for last year?
Was Galchenyuk a defensive stalwart last season? Did he have a defensive game in 2014-15 that's regressed this year?
So really, I'm not seeing any substantive difference between 2014-15 and 2015-16 that let's me clearly see why one year moving Galch is bad, but this year it makes total sense.
Simple explanation: last year, the team was winning and Galchenyuk was not -15 over 4 weeks. This year, the team was losing and the red light kept lighting up behind our goalie. After four weeks of that, the coach is entitled to adjust.
As for the line juggling, actually Galch remained at center for a long time after Gallagher went down. He was finally moved to wing recently, at the same time Eller was moved to C.
In reponse to Kriss E, it is true that I said that moving Galchenyuk to wing was necessary if we wanted him to play 16-18 minutes per game. Just because Therrien did not often do that does not mean that I was wrong.
Here is what I would like to see, if there were no injuries.
17-19 minutes
Galchenyuk-Plekanec-Gallagher
15-17 minutes
Pacioretty-Eller-Andrighetto/Carr
11-12 minutes
Carr/Andrighetto-Desharnais-Weise
Byron-DeLaRose-Mitchell/Flynn
Pacioretty could pick up a couple extra minutes being double shifted at the end of a period.