Trollbox is too weak to really matter.
It definitely shouldn’t screw with investigations, just look at the title of the thread.
And of course, you can take out a Fool with a Knight, Prince, or even the King if you suspect them.
My biggest objection is Frame and nullifying the day phase.
But I’ll say once again that Fool isn’t a rival. It is most definitely harmful, but killing the Fool is not killing an enemy. You’d always kill an Assassin over a Fool. Fool is inconvenient, not trying to work against you.
Besides, it’s fun to play as, and it makes the BD more cautious, which isn’t a bad thing. Even it’s use as a crutch for new players ultimately makes the game more fun.
While the implementation may be sub optimal, the concept isn’t bad.