Hersh was sadly lost all credibility as he's gotten older. Just look at the quality of the publications he writes for. He goes down a notch every major story he covers. It's a sad end to what was once a well-respected journalist.
Leave Seymour Hersh aside. Do you have any doubt that Seth Rich was not the Wikileaks DNC source? Even before Seymour Hersh, a few people had hinted at Rich's involvement. It was Seth Rich, and that was why he was murdered by the goons of Clinton.
Not sure what you mean by "Leave Seymour Hersh aside". Are there any credible sources for the claim? When a journalist reports counter to virtually all mainstream reporting, without providing one shred of evidence or on the record quote, all you're left with is the reliability of said reporter. In this case that's Hersh.
As far as any doubt-yes, there's plenty of doubt. That's what you're left with in the absence of clear and convincing (or really any at all) evidence.
