> They have leaked information that mass media would otherwise not have been anywhere close to exposing.
Is there a specific case you're thinking of? For instance, with the DNC leaks, or with Chelsea Manning's leaks, I believe that the information relevant to the public interest would have been disclosed by any reputable major news outlet (NYT, WashPo, ...) that received it, so long as its authenticity could be verified.
I prefer that leakers go to traditional journalists (à la Snowden) rather than WikiLeaks. WikiLeaks has a track record of creating collateral damage with its disclosures; for example, exposing SSNs and credit card numbers of people who happened to be donors to the DNC and who were otherwise uninvolved with the shenanigans going on. A responsible, ethical journalist would take care to exclude personal information that is tangential to the actual public interest.