In Australian law, the threshold is simply that there is an honest and reasonable belief, or that the conduct or information actually shows wrongdoing, irrespective of the subjective state of mind of the whistle-blower.
People can disclose information where they really don't understand its own significance. It might be a minor fraud, but this might be evidence of massive corruption that they don't even know about. I think basic tests of an honest and reasonable belief more than do the job. For the same reason, Australia is systematically removing any good faith requirements from its law, as is being done in the U.K. and elsewhere.