Categorization Strategy for Meaningful Reporting

Summary

What is your strategy for coming up with category values?

Content

I am the PM for a large implementation of OSvC that serves the internal sales force. We provide support for a long list of globally used sales applications. In the past, we have tried analyzing our historic requests and coming up with many categories that fit the comprehensive list of issue types we've seen come in. What we found was the more categories there are to select, the more likely the agent is to select wrong. If there is a "catchall/issue not listed" category available, many agents always use that. This renders our category reporting useless.