Thanks for the info Russell. I am sorry you had to gave up. I just tried to play with the Workshop and I believe I achieved what you described though. Let me share what I did.
In the course, I have one user enrolled as the Teacher, two users enrolled as Non-editing teachers (those will do the actual assessment so you can think of them as your Markers) and couple of users enrolled as Students (those will submit their work). I am logged in as the Teacher who is considered as the co-ordinator of the whole activity here.
There are two groups in the course. Each Non-editing teacher has membership in one of them. My plan is to let students submit their work and then let the work assess by markers.
I created Workshop instance in separate groups mode. The setting "Use peer assessment" does not have much impact in Workshop yet. It is planned that in the future, if this feature is disabled, the user interface would be simplified (or, the setting will be removed eventually). Anyway, I left all three workshop features unchecked.
Then I followed the Settings block > Workshop administration > Permissions and locally overrode permissions. I removed following capabilities from the Non-editing teacher (Marker) role:
- Access all groups
- Allocate submissions for review
- Manage example submissions
- Switch phase
- View all assessments
- View all submissions
and I added the role Non-editing teacher to the list of roles that can "Peer assess". And finally I removed the capability "Peer assess" from the role Student.
Students were able to submit their work as expected. To allocate their submissions for assessment, I used the Random allocator. I had to check "Participants can assess without having submitted anything" of course because the Markers did not submit anything. The random allocator picks users with the capability "Peer assess" and allocates them as reviewers (assessors) of submissions. It respects separate and visible group mode so that each Marker received only submissions from their group.
The Manual allocator can be used, too. But as you experienced, it is not intended for large scale groups like you have. For these scenarios, the Random allocator is expected to do the job.
You are right in that the Manual allocator (the one with pull menus) does not obey group mode and even the locally overridden permissions. It may be considered as a bug and I will appreciate if you report it in the tracker.
However, I was able to log in as the Marker and see just assigned submissions to assess. As I was afraid, the UI is not optimized for this use case much yet. For example, students can still read "You have no assigned submission to assess" during the Assessment phase.
Summary: I do not agree much with the workarounds you suggested above. There is an advance setup of permissions available that supports your scenario. And submissions should be allocated using the random allocator in this case, the manual allocator is intended for smaller groups.