Major Description
When you are on a node that does not have the query service, you are not authenticated with the other servers in the clsuter as far as the query service goes. So when you go to the query workbench it gives you an error that you cannot do that here and must go to a node with the query service running.
As part of that error, please explain in that error message why this is. Please give a 1 to 2 sentence explanation about security limitations, etc. Nothing too deep, but at least give the user a rationale.