Have you tried to use the Responsibilities Endpoint:
https://[enviroment].data3sixty.com/api/v2/responsibilities/assignments?_assetUid=[UID OF METRIC]
This would quite happily give you all the responsibilities for any Asset, including metrics
You get the name of the responsibility, the name of the person, the UID of the person. Everything you need.
The nested JSON is able to handle as many assignment you might have.
Try connecting to the endpoint in Excel and use Power Query to help parse the JSON and expand the nested JSON to rows. You will get repeated Asset UIDs for each responsibility, which you can then throw into a pivot table and create a lovely display.
And zero need to export a file as its already in Excel.
You can even run a separate data source of the Metric Endpoint to bring in the information about the metric and merge the data on the Asset UID, created a pivot table with Metric information AND the ownership.
Hope that helps.
John