My name is Joe Morel and I'm a Program Manager on Telligent's Product team.
I agree with you--this is a shortcoming of our current release. We only expose reputation data about individual people, but do not expose any "top users" lists. We did this because we have been pointing people to use Telligent Analytics for people-comparison, because it is so much more powerful than a simple list of people.
The use-case missing from that is exposing top user information to end-users. This is something that we are tackling in the next version of our product because we recognize that it's a pain point for our customers and we want to make it better.
The "Top Members" widget is our obvious suggestion for now, but it obviously doesn't work in joinless groups.
Just trying to be transparent--this is something we could do better, and I appreciate the feedback and sympathize with your frustration over this issue.