When executing the following cmdlet from a workstation with the Active Roles Management Shell installed, the run time is about 7 hours, same script running on the Active Roles server takes about 25 minutes:
Get-QADUser -SamAccountName $samAccountName -DontUseDefaultIncludedProperties -LdapFilter "(!(extensionattribute7=full))" -SearchRoot "ou=Test,dc=DomainName,dc=local" -Proxy
The above cmdlet takes on the ARS server 417 milliseconds, and if executed from a workstation, it takes 13,888 milliseconds (measured by the measure-command cmdlet)
There might be another administration service kicking around somewhere further away than the one it is running on. By adding the -service switch, it's specifying the host. Without it, it will use the service connection points and could very well be selecting one on the other side of the globe.
Workaround: Use switch -Service