I have even heard a prominent CPAN contributor say that testers reports without verbose output are useless

I'm a little surprised by this comment. Tests reports, even without verbosity, include the details of failing tests, such as its label, line number, and any diagnostic output.

My own experience developing CPAN::Reporter and other modules is that almost any test report is helpful. The exceptions have been some issues with CPANPLUS where no details are provided, which I think had to do with Module::Build support. (I don't know if that has been addressed, and frankly, now that CPAN.pm supports Module::Build and does test reporting, I've stopped paying attention to CPANPLUS.)

Nevertheless, verbose reporting is an interesting idea and I'll put it on the Todo list to add as a configuration option.