Some years (and Moodle versions) ago, Web Services decided to remove the Workshop module/activity as an option for instructors on our Moodle site. Many users found this tool complex and unreliable. In part because Moodle 2.8 has limited alternatives for peer review of assignments, we have reactivated it indefinitely on a trial run.
The Workshop module is designed to
navigate students and the instructor through an extended process for peer grading an assignment. The setup and navigation of the module can be
tricky and tedious, but it does offer capabilities that don't exist elsewhere in Moodle.
If you'd like assistance in making the Workshop a success in your class, I'd be happy to collaborate with you. It would be nice to know if this feature can be used as a pedagogical plus. I demo'ed it myself, felt like it worked, and exited the process intrigued.
You can read the MoodleDoc on the Workshop