You may have noticed that the Up and Down arrow buttons not visible in Edit domain connection -> Advanced settings tab:
This is a product defect (TF00786661).
Use the different scroll bars to see/access the Up and Down buttons. Or manually re-add the DCs in the desired order.
This will be fixed on a future release of the product. Please refer to this article for updates or contact support referencing the defect ID TF00786661.