I have created new moosh command you may be interested in: audit-passwords. It will try all the non-deleted user's passwords against top 10 000 know passwords and report if any of your users uses one of them.
The command runs against all Moodle versions from 1.9 up. For latest Moodle versions with new salting (2.5 and above) you should expect it will take quite some time to run full scan - expect something like 10 minutes / user .
% moosh audit-passwords
User with known (easily crackable) password: admin
-r option will show the matched password:
% moosh audit-passwords -r
User with known (easily crackable) password: admin / qwerty