You're conflating leakers and gossipers as bad. If they're operating under #2 in my list, their motives wouldn't be considered bad, though perhaps misguided.
I think your definition is of a whistleblower is too narrow, and I prefer the fuller definition from wikipedia:
"A whistleblower (also written as whistle-blower or whistle blower)[1] is a person who exposes any kind of information or activity that is deemed illegal, unethical, or not correct within an organization that is either private or public."
"not correct within an organization" clearly applies to the #2 in my list.
