I played him for the first time since the beta today. I got burned out on using him all the time to practice in the beta, so I've avoided him until now. It may just have been the map size (Franzea), but I was only able to get 3 kills per level 2. I still won easily, but I remember being able to bag 6 at a time in the beta. I guess that is kind of too powerful though.
It lasts the same duration. The only reason why you were able to get more than 1 kill per player is because people were probably pressing attack buttons during their respawn invincibility states (ends the invincibility prematurely). Parappa's super can't score more than 1 kill per player against competent players (even in the beta). Just doesn't last long enough.
I've gotten five kills in the game with his level 2.
It's not easy. I basically killed all 3 in a row as soon as I started the super.
Then I got the next two when they were next to each other. It was on Hades
Exactly how my situation went out, 5 Kills and got those 3 instantly and it was on Hades haha.