I think the habs exposed a problem with corsi last year. There are high danger chances and then there are "complete breakdown leaving goalie with no hope." The habs were generally not great but there were long stretches where they would give up a goal or two a game that were of a type you normally don't see in the NHL where the coverage was so completely messed up that opposing forwards would be able to pass across the crease with no one to interfere, they could toy with the goalie. The team was playing at a level way below NHL standards and it skewed save percentages, shooting percentaged and so on. Corsi is a good indication if the teams are playing similarly, if one team is totally confused and allowing easy tap ins it is less effective.
If they haven't worked out the system to prevent this, with or without Weber, the habs will not only lose again they will actively make their goalies worse. I don't think any goalie can keep a good mental state when they are completely exposed this way. Niemi did better than Price and Lindgren but then he came in later in the year when the team was allowing a lot less of those goals.
I expect the problem was a combination of high turnover, low skill, and changing systems. They ditched a lot of good or at least dimensional players (Emelin could hit, Beaulieu could skate, Markov could pass, new guys could sort of handle third pairing minutes, maybe) and brought in loads of third pairing players. Julien's system is very different, from Therrien's, Therrien went for simplicity and effort, Julien wanted complexity and stuff that the players, and possibly the assistant coaches, could not figure out.
If they don't work out the system the personnel does not matter. And players who leave Montreal will look just fine after they leave, just like last year. Morrow looked horrible here but he was OK on a different team. I'm sure Price would go back to good stats on a better team with a D that would not hang him out to dry.
Petry's advanced stats looked OK last year, it looked like he was unlucky and eventually the goals for % should catch up, but the habs were so inept at playing the system Julien tried to install that a low shooting percentage and a low save percentage were to be expected, and can be expected to continue. The advanced stats give false hope.
Was Markov the most effective defensive coach last year? Will the new assistants work things out? We'll see...