Great post mesverrum, thanks for sharing.
I would also add that a good starting point would be to make the classification based on a list like Audit Policies and Best Practices for LEM - SolarWinds Worldwide, LLC. Help and Support
We reduced it further by fine-tuning the rules, correlation, correlation time and applying internal-specific filters. We only track around 20 Windows categories and the rest are stopped at source level, they do not reach LEM.
I would advise you to also set up Scheduled Search reports, more flexible than LEM Reports.
They can be set up quickly and once you configure them properly with LEM actions, you can also delegate the reporting to appropriate personnel, so they're "in the know" about specific events of their interest.