It seem that the CIA has been, at best, a weak performer, at worst an actual menace. I can understand that the reason they made the CIA separate from the FBI was a fear that J. Edgar Hoover would turn it into his shadow Empire, as he did the FBI. Heck, the FBI still managed to pull off CIA style dirty tricks under cointelpro, as MLK's family can tell you.
However, perhaps the problem is that the CIA is separate; they know they account to no one. If we folded them into the FBI, making them the MI6 to the FBI's MI5, could that help get a better class of agent, or at least, one more accountable?
1. We can do anything. It's unlikely that we will, though.
Petraeus reported to DNI James Clapper--he was the guy who urged him to submit his resignation. They do have oversight...such as it is. There's also Congressional oversight, though it is sometimes after the fact.