I agree with a lot of people here. Investigator seems misnamed and the flavor is a little lacking. When I think of investigator as a hybrid class like this, I immediately think of a bard/rogue. Heck, even alchemist/bard seems to better fit. I definitely think this is better class with the bard's knowledge based abilities blended with the rogue's stealth oriented game play. Alchemist/bard could capture the idea of a forensic investigator, using science to determine causes of death and such.
Alchemist/rogue for me just does not scream investigator to me.
As well as this, the investigator does not, in my opinion, does not do enough to create a fully unique experience or even a truly unique class. Unlike the other classes, it feels simply like a gestalt alchemist/rogue. The inspiration talents are interesting, but they are, again in my opinion, thinly veiled rogue talents. I would also decrease the amount of die for sneak attack, while it is one less than rogue, it still steps on a full rogue's toes.