I never use definition groups for data migration purposes. Instead
I write my own scripts using AIF for data migration. One advantage using AIF is - the framework will take care of all underlying data validations. All that requires to be done is to pass the necessary parameters.
Of course in versions before AX 2012, it is possible to directly insert data into tables by X++.
Irrespective of whichever path we choose (from the two options above) it is a developers job.