Remember: It's the playoffs, and the league's rule of thinking is that one playoff game is equal to two regular season games. So, in their mind, they essentially hit Prust with a four game suspension, which would be about average for this type of play.
From my own perspective, that's about right. Clearly, it's interference ... the puck is well gone before Prust follows through with his hit to Derek Stepan. But, the primary point of contact (and that's important, according to the rulebook) was the shoulder/chest. Stepan's head snaps forward, causing his chin to make contact with both Prust's shoulder and his own chest, which is where I'm sure he broke his jaw.
Is it a suspendable play? Absolutely ... but, it can't be classified as targeting the head, because the head wasn't the primary point of contact. Of note, the suspension reason is listed as "interference".
I think they got it right.
As for the suspension to Carcillo and Prust being deserving of the same length ... no, that's just wrong. Carcillo's suspension carries an automatic 10 games, and rightfully so. He hacked a referee in the legs and then threw a glancing blow at his head. The ruling there is absolutely justified - playoffs or not.
