First of all I want to add to ale's question that the migration from Super User to Web Applications is frequently wrong both ways, that is that obvious migration candidate questions about Gmail or Facebook are mistakenly reviewed at Super User as off topic because "This question is not about computer hardware or software, within the scope defined in the help center." so that a question that should be migrated to Web Applications isn't migrated.
What I could do to help solve the problem is to discuss the matter with the individual reviewers in a Super User chat room. When facing difficulties reviewing borderline questions I have obtained good results from asking other reviewers for advice about how to review the question in chat.