This is of course a question of opinion and judgment, about which reasonable people might disagree. But I can at least talk about some of the pros and cons you might want to consider when answering this question.
There are currently 17---seventeen---distinct US federal intelligence agencies. The ODNI and CIA are independent agencies, the OICI is part of the Department of Energy, the I&A, CGI, and HSI are part of the Department of Homeland Security, the TFI are part of the Department of the Treasury (I actually know someone who worked for the TFI, as it turns out---but I wouldn't be surprised if you didn't even know it existed before today!), the DIA, NSA, CSS, NGA, NRO, NASIC, INSCOM, NGIC, MCIA, and ONI are all part of the Department of Defense, and the FBI and DEA are part of the Department of Justice. That's not even counting a lot of other agencies like the ATF and FEMA that have very important roles in national security but aren't strictly intelligence-related.
This huge proliferation of agencies (and acronyms!) surely introduces a lot of inefficiencies and redundant activities. Several times now there has been a terrorist attack that one agency knew about (say, the CIA), but failed to inform the agency that would be responsible for preventing it (say, the FBI) in time to do anything about it. Consolidating these agencies into a smaller number (say, just the FBI, CIA, and DIA) could dramatically improve response times and thus strengthen national security. It could also save a good deal of money; we spend tens of billions of dollars a year on all these agencies, and much of that is being spent to pay staff to do things that have already been done by other agencies.
On the other hand, there are advantages to having such a large number of agencies, advantages that in a sense speak to the national character of the United States itself. We're all about freedom, competition, and separation of powers, right? Well, having many agencies instead of just one or a few means that we have competition between agencies. It means that the NSA can check up on the FBI and the HSI can check up on the NSA. In theory, it means that any agency that steps out of the bounds of rule of law and violates civil liberties, or any agency that has widespread incompetence or corruption, will be revealed by the other agencies. (Has this actually happened? Your mileage may vary.)
I don't mean to red-bait here, but one thing that really did strongly distinguish the KGB from US agencies was how unified the KGB was; they handled almost everything, foreign and domestic, military and civilian. The KGB was in many ways a more efficient intelligence agency (Soviet spying was clearly the best in the world; the US and UK were actually quite distant second and third); but it was also far more oppressive to the civil liberties of the Soviet people. That's clearly not the only reason of course---I'm not saying that if we aggregate our intelligence agencies we'll suddenly become Stalin's USSR. But there may be some real connection here: Perhaps part of why it was so hard for anyone to escape the eye of the KGB was their unification of all intelligence services into one. Having many agencies is inefficient---but perhaps that's exactly what we want.
On balance, my humble opinion is that some consolidation is in order; 17 is too many, perhaps we could do with 8 or 5 or even 3. Part of that reorganization might mean integrating the CIA into the DHS (though honestly I might do away with the DHS altogether; its function is too nebulous, its name is too Orwellian). But I would not want to risk integrating all intelligence services into one.