Chances are, problems get into a queue that is served in order of priority, and a careful process for rating importance will help you focus on resolving problems rather than on defending your methodology. Allowing management to decide which problems get handled first without any reference to the set of all problems or the pool of available resources will interfere with productivity. The second step is judging the priority of the problem. Priority describes an assessment of the importance of a problem. Critical items should be tackled first, because the effects of such a problem cascades down the site's functionality and infrastructure.
Any problem interfering with a major site functionality is a high priority.
Any problem that will make you or your site look stupid or incompetent or untrustworthy is a high priority. Every severity level has a corresponding default priority level, but priority allows for some input from human and business needs. Problems with greater scopes should be addressed before lesser-scoped problems, regardless of priority. I will use the severity as the basis for this new scheme, since scope is a more qualitative measurement of importance. As you can see, this new ranking allows problems with a lower severity but a higher priority to be moved up ahead of problems that have a higher scope but lower priority.