Hello Lance,
Thank you for the reply. You've presented some excellent points, however it looks like I've checked all those boxes so far. Here's some more information:
1. The observed behavior is not client or WAN/Internet specific. All clients see the same result (Web GIS, ArcMap, ArcGIS Pro, other "thick" clients consuming the OGC service sub-types.
2. Confirmed. Mosaic Data Set is source for all services. All paths repaired in all MDS after the data move. The data move was done summer 2020, so if there were any path problems, I would have expected those to surface a while ago.
3. Confirmed. ArcGIS Enterprise server role Image Server
4. Confirmed. Fully Qualified Domain Name (FQDN) paths used for all connected resources. Although the move of our native orthoimagery tiles changed the FQDN from \\the.original.path\gisdata to \\the.new.path\gisdata, the underlying folder/file structure is exactly the same. The pathing is really pretty simple: From ArcGIS Enterprise Server to Enterprise storage using a single MS AD service account with R,W,E permissions on both the server and the storage.
5. Confirmed. No consistent timeouts, low latency on all services. I'm running ArcGIS Monitor so I have months of historical data to lean on here.
6. Confirmed. No local cache. All services dynamic.
7. Confirmed. Some image services have had the MDS re-analyzed and have been republished. No apparent behavior change.
Thank you for the feedback.
Todd