Update: AAD Connect Network Test Tool
I trotted out the trusty WireShark and Fiddler tools today and ran through the latest iteration of AAD Connect setup. In so doing, I've added a few endpoints to the test:
$RequiredResources
adminwebservice-s1-co2.microsoftonline.com
$RequiredResourcesEndpoints
https://adminwebservice-s1-co2.microsoftonline.com/provisioningwebservice.svc
As always, the newest version is available at https://aka.ms/aadnetwork.
Goodnight and good luck!