If you ever run into a "discovery: SOAP Response cannot be decoded. Raw response: " trying to delete, edit, merge, or repoll a device, follow these steps to resolve the issue.
The CA NFA Collection and Poller Web Services may be in a hung state.
Component : NQRPTA - REPORTERANALYZER
Restart the CA NFA Collection and Poller Web service on the NFA Harvester the device belongs to. This should resolve the issue.