By default DxDesigner does not use net name delimiters so a bus named Data(15:0) will have nets as seen by DxDesigner of Data15, Data14 etc. The migration checks are really aimed at migrating from pre-iCDB versions of DxDesigner, not from other tools such as Design Capture. This check and resultant errors can be safely ignored for bus members coming from Design Capture.
As a note; If you require your nets to be delimited by either () or  in DxDesigner, ensure it is set up appropriately in Settings - Boards - Net Name Delimiter. Setting this accordingly does not remove the errors from DRC-002 though.