This suspension was pretty cut and dry for Brendan Shanahan's office. Grabner pretty clearly picked Gerbe's head (insert joke about Gerbe being small and there being no other place to hit him here) and little else in his hit. Not only that but he came across the ice to deliver the hit.
It ends up only being a two-game suspension thanks in part to the fact that Gerbe was OK, luckily. We've seen hits similar to this turn out much worse for the player on the receiving end. Not to mention Grabner has no prior history of supplemental discipline, another factor working in his favor and thus leading to only two games.
For the two-game ban, Grabner will also surrender $30,769.24 in salary.