Will this work?
Create a file geodatabase (FGDB) and add your featureclass and table. In ArcMap, import your featureclass and table. Join the table to the featureclass and make any symbology changes you wish. Save your map. Now, from ArcMap, create a Layer File (.LYR) of your featureclass and consume the LYR file in ArcGIS Explorer. See attached.
If the FGDB is accessible to the ArcMap owner and AGX user, then the ArcMap person can make changes to the featureclass and/or joined table and the results will be available to your AGX end-user.