Updating just the Routers table wouldn't also trigger an update on the interface level as well.
Updating the domain from the GUI will trigger an update every
There is a domainID in the interfaces and agent_definitions table as well that would need to be updated and perhaps elsewhere.
Missing an update to the domainID in one place could leave orphaned records and cause unforeseen problems.
I would recommend the following:
1. Go to the Admin->Physical & Virtual page.
2. In the search bar, search for the Harvester address for these devices.
3. Expand the "Max Per Page" to 200 devices.
4. Click the check box to select all displayed devices and select "Edit".
5. Change the domain
This will knock out 200 of your 250 devices in one shot. Then just repeat for the other 50.