When solr has a large number of fields, the views admin UI becomes un-usable.
The root of the issue is drupal views doesn't page the fields data, instead it pulls everything at once causing the browser to crash. The issue isn't the luke request handler. It has no issue returning 5000+ fields.
2 options come to mind.
1- submit a patch to drupal core to page field data
2- create a solr settings interface to select which fields are available to views (or all solr related functionality) so we're not dealing with a copious number of fields. In my case 5600 fields (dgi basic solr config XSLTs).