*Nothing* gives us the full picture -- that's a silly standard to hold anyone or anything to. In fact, there's no such thing as the "full picture" -- the "full picture" is a platonic ideal that doesn't exist in real life.
Whistle blowers don't give us the full picture. That's true. They do
obviously give us a fuller picture than the military and intelligence press divisions. They're also a vital piece of the media's ability to give us anything resembling the full picture.
Would you prefer every news outlet just politely ask the DOJ if they're doing anything illegal on page 1, and paraphrase NSA press releases on page 2?
As long as there are filthy rich and deeply secretive organizations who are in the habit of breaking the law or bending it for unjust ends (which is to say for the foreseeable future) we need
whistle blowers and others willing to break unjust laws themselves for the greater good.
The unchecked secrecy of our defense and intelligence agencies is a great threat to freedom and justice. This state of affairs may have been deemed legal, but it is a grave mistake to confuse legality with moral or ethical acceptability -- or to place law above ethics. As MLK wrote: "One has not only a legal but a moral responsibility to obey just laws. Conversely, one has a moral responsibility to disobey unjust laws."
I'd still love to hear how else you think anything can or should ever get out of the black boxes that our defense and intelligence agencies have become. It's easy to criticize whistle blowing, but it's also pointless unless you're offering a viable alternative for finding out what evils the most powerful organizations are up to behind closed doors.