I know this thread is a couple of months old, but I just started dabbling in this.
I actually have RSAT (Active Directory Users and Computers connecting to my freenas host with it's domain settings enabled. But there are certain options that I just can't seem to change. For instance if I try and change a users name in the "Account" tab I get a slew of errors...
"The Specified Domain either does not exist or could not be contacted"
"The pr-Windows 2000 domain name for the user cannot be displayed"
And other things around that...
But ADExplorer works beautifully....
https://technet.microsoft.com/en-us/sysinternals/adexplorer.aspx
The only issue with it, is you can't reset passwords (As far as I know...).... Still playing around with everything!