Kevin was kept to a minimum, he didn't sit in on the meetings etc. Vikki was shoved down the viewers throat.

The actress that played Vicki was sleeping with NBC executives. NBC then forced the writers of Just Shoot Me to add the actress as Vicki to the show. She had very little talent, and could have ruined the show but finally she was written out halfway through the season. By then the damage was already done, and the show was cancelled.

I also liked Kevin a lot. His humor was great.
The KEY difference between him and Vicki though, is that his role was kept to a MINIMUM. Vicki was clearly supposed to be part of the "TEAM" of Jack, Elliot, Dennis, Maya, and Nina.
An unnecessary addition, ugh. She sucked. She brought nothing.