Lets not over sell Kovacevic, Harris, Pearson and Ylonen's contribution to the team. You wont convince me that adding Dach, Laine and Hutson over any of them is a downgrade in either skill or impact on the locker room.
As far as Allen got, I can see how this can play on Montanbault's performance, but Monty is 27, not a rookie anymore. He shouldn't need a vet to help him. I will give you Monahan be a huge lost. That said, the team after last year TDL didn't play like it does right now.
You are right that this team is very green, I think it the youngest (or close to) in the NHL. So mental breakdown are to be expected. That is why I said I dont think you can turn this thing around quickly. I said in another tread that my first move would get rid of Dvorak ASAP. To me, right now the only thing you can fix is the work ethic. If that isn't fix you wont be able to address any other aspect of the team. If you can get them to work hard, some lucky break will come their way, this will boost confidence and help them buy into the system.