I don't think either Gan Ning or Cao Caro are really inactive, everyone has crap they do outside of the game and throwing the blame on someone due to inactivity is only useful when they post only enough to keep them from avoiding suspicion. I don't find gan ning to be suspicious as much as I used to, he may be mafia but I personally doubt it. Currently Zhao has had some decent points being made and as of yet does not have too much suspicious activity to take note of.
For some reason I'm really starting to think that Cao Cao is mafia but I still need to look up the evidence I have before I vote so I know my reasoning for being suspicious.