Fenton hired Evason to be an assistant under Boudreau, obviously to try and ruffle BB's feathers. BG fired BB even though he was on a decent winning streak, and decided to try Evason, a lifelong Asst/AHL head coach. He's had good results in the regular season, and has some respect in the dressing room among players, but his teams have usually been poor/mediocre on special teams, FO's, and in the playoffs.
He's basically an average coach. Up till now you could argue that he has been an above average coach, at least in the regular season.
Because of the cap penalties this year and next(thanks, NHL), it's going to be near impossible for them to win anything of note, or attract a top coach. I think they'll try to drag out firing Dean for as long as possible. Loud, sustained booing, and unsold seats will be the thing that will force changes. They might start with firing an assistant coach, or making a small trade to shake up the room.
Guerin has done some good things since coming here, but he has also made some unforced errors. I blame him just as much, if not more, for the present state of the team, as Evason.