How do you try to not go insane in some scenarios that give automatic horror with no test? We played one scenario (you investigate the town on 3 separate days, Innsmouth maybe?) and after each day you are given automatic horror (1, then 2, then 3 after each day). If you do not have a way to heal horror (not something you can control) then any investigator with 6 or less starting sanity WILL be insane at the end, guaranteed. If they then draw a traitor card, either they must play against the goal (NOT fun for my gaming group as we care about experiencing the story of the scenario) or they ignore the card and then what's the point?
Regardless, I don't claim that it's a broken mechanic and if you like it then great for you but my group HATES them as it ruins OUR idea of fun. I don't understand the desire to argue one idea of fun is somehow better and more pure than another. The OP hates the traitor cards and probably hopes that FFG will provide an official variant (a sentiment I agree with as I feel this game is almost perfect otherwise <- opinion in case that wasn't clear). I loathe traitor and semi-cooperative games but love almost everything else this game brings to the table. So, while I generally avoid houseruling games, I make an exception in this case as otherwise amazing gaming experiences can occasionally be ruined <-opinion warning.