Arber needs to improve his game. I'm the first to think that given the skill set of the players MTL has, they need a player like him: mean, physical shut down first guy.
The way I see, and I said as much in another tread, Arber is stuck in between two role: the very responsible defensively dman and the enforcer and he's not succeeding in adapting. Part of this is due to MSL asking him to pick is spot for hitting and getting penalties. Now combine that with how the Refs are behaving with him. They are so concerns that things may get out of hand around him that they more often then not enforce the rules more stringently with him. This leads to him getting more penalties, and that must play in his head. If I was him would would be "F. this... nothing I do is ok".
That said, he need to play better too. How many of these one hand passes/push the puck to his d partner as he done? He make "lazy" plays at time. He need to be more engaged and take control of the play: assert physical dominance, create time and space, control the puck, make smart play.