Ive always seen Crowded House as very much Neil, Nick, Paul and Mark. Then, with Paul no longer with us, Matt.
In terms of importance, certainly live I always thought of Mark as almost irreplaceable. His grungey kind of guitar style mixed with all the work he does on synths, lap steel and harmonies always stood out. But more than what he played its how he plays it that makes him difficult to replace (and why hopefully I can get him to play on some of my stuff 😁)
I might be wrong as well but for some reason I wonder if there was a touch of professional animosity between Mark and Mitchell Froom as I remember reading somewhere that Mitchell kind of sidelined him in recording the 3 added recurring dream songs. I know myself as a musician that would get my back up a little, especially with the obvious sound contributions he made to Together Alone.
I also think as well for the most part when you think of Crowded House you think not only of their music but of the persona of the band, the piss taking, the messing around on stage and the banter. When something like a suspected sacking takes place it refocusses things and makes it feel more 'business like'
I dunno, I'm just kind of thinking out loud here but the one big take away for me is its gonna be a real shame not seeing but more importantly hearing Mark up there.