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.
What was the actual, observable impact of unabridged Wikileaks documents in court cases?
WikiLeaks is a media organisation so it will crave for attention as all media does. But please name one single case in which data released by WikiLeaks was bogus.
On the other hand I could bring up hundreds of cases where main stream media has released fake information.
So how exactly do you decide who has credibility and who does not?
I too doubt that they have anything that significant for the election but I will give them the benefit of the doubt based on their prior important work. I also understand that they release information bit by bit. If it was released all at once, mass media would not have a chance to report on all of it.