I think you have to hold someone responsible for illegal actions that lead directly and predictably to injury. Malice intended or not, it is a reckless play. I might just make it one game, but would make it clear "you can't do that"...otherwise the message is "Granlund, you can't play here".
If Buff did the same thing without the proximity to the boards, I would be more inclined to think it was not suspendable given the same injury and result, even though still illegal, as it would not be near as dangerous and more towards accidental.
I know this was not a concussion, but when the class action suit is in full gear, this clip can be used to show what the NHL considers a nonsuspendable 2 minute penalty...