I think there's a couple ways of keeping this in.  We could either:

1. have AssessmentRequest objects touch the Submission object they belong to when they are updated, or
2. we could add @current_user_submission.assigned_assessments to the cache key

The first way has the disadvantage of clearing other submission caches, but the second has the potential to create very long cache keys.  In practice there will almost always be 0-3 assigned_assessments, so I think I lean toward option 2 a little.