I agree with respect to Niskanen. I can see why the 5 and a game was called - at full speed in real time and a player lying on the ice, a ref is very likely to make that call. 
The call that was missed was Ovechkin's wild 2 hand slash that started the series of events.
Hockey has become dangerous because players are larger, stronger and wear hardened armour to protect themselves. Ovechkin regularly drives through players with reckless abandon and no regard for their safety. Clamp down on the stick work and (as much as i hate to agree with Don Cherry) get rid of the armoured equipment - shoulder pads and elbow pads. That will slow players down. 
Also bringing back the Charging penalty might help. Used to be regularly called for any check where a player took more than 3 strides and/or left his feet. 2 minutes for charging (or 5) is almost never seen anymore.