Sorry if this is the wrong place to post this but I am having the very problem exposed above. Several professors grading the same activity and each one of us wipes up the grades imported by the other professors because all of us have "null grades" for the students we don´t grade.
We currently have Moodle 2.4. Was there a workaround? Has this been fixed in later versions or will I have to wait til 2.8 with "Force Import" (and will that fix the issue) ?