Support case was opened and the following resolution provided:
The 'imexutil' utility is only available on DE Server (manager) installations. On a non-manager machine, you can install the Agent (includes agent and espmgr utility), the CLI (command line option to run some commands, but not import/export) and the Desktop Client (which includes the CLI perspective but not imexutil).
If you have imexutil running on your System Agent r7 machine, you must have installed a DE manager there. Sure, you may be using the imexutil to connect to the 11.3 DE server remotely, but there must be some DE manager installed locally as well.
Now, for DE 12 you can only use the imexutil for version 12. It is located on the DE 12 server. You cannot do export/import from another machine unless you install another DE 12 server there.