If anyone thinks that Snowden should have tried harder to use “official channels” to make someone outside the NSA aware of the issues he exposed, here’s an article from Reason, a libertarian/conservative publication:
It describes the ordeal of William Binney, who tried to do just that, concerning almost identical issues.
And from liberal Conor Friedersdorf at The Atlantic, http://www.theatlantic.com/politics/archive/2014/07/the-pattern-of-persecuting-dissenters-in-the-national-security-state/374051/
stories of Binney and also CIA agents who tried to expose wrongdoing using the channels provided within their agencies for exactly this type of thing.
They all ended up being fired, and their houses and families raided, and frequently charged with crimes that were based on their following of the whistleblower rules.
Whether or not you agree with the material Snowden has exposed, there is no doubt that he did it in the most expedient and effective way, and it would not have gotten out otherwise.