I never understood why ArcGIS uses domains when it could just use tables from the underlying database. If your geodatabase is built on top of Oracle, then you should be able to just choose which table/field is the appropriate "domain" for the field you are creating. In this way, when you update the Oracle table in some other app, the changes can be automatically applied to the geodatabase (using versioning, etc. when necessary). The fact that ArcGIS uses domains means that ESRI now has to build all these tools in order to edit the domains and it's very difficult for other apps to have access to that data (even read access, nevermind write access).