Possible performance issue with iRule?

1. Since you have no default for the switch you have no way to tell if some URI's are failing to match. You should add a default which logs the unmatched URI as they will fail to get a response if no pool is selected...

switch -glob [HTTP::uri] {
      "/ee/employer*" { pool Pool_ee_employer_83 }
      "/ee/search*" { pool Pool_ee_search_84 }
      "/pack*" { pool Pool_pack_85 }
      default { log "Unmatched URI [HTTP::uri]" }
}

2. If you are switching pools then you need to make sure that the CSS page from one pool will work on page elements from different servers. Often CSS is designed to match the content coming from the same web server or pool of identical web servers.

3. You should be using HTTP classes instead of an iRule for this. Ensure that you add a default catch-all class at the end.

Start with the logging as that may provide some clues.