c_value is not required, so unless you plan on using it, it does not need to be present. It is supposed to be a classification_view https://developer.omniture.com/en_US/documentation/omniture-administration/r-classification-view.
It takes some trial and error to get this api working. Here is an example of a call I use that works using the REST api over Java:
Request:
{
"check_divisions":1,
"description":"Report Test 1",
"email_address":"cdegroot@adobe.com",
"export_results":"0",
"overwrite_conflicts":0,
"relation_id":65,
"report_suite_array":["cdgdev"],
"header":["Key","Survey","Survey^Question","Survey^Question^Response","Engagement Index","Survey > Question > Response"]
}
Response:
"3387166"
Kind Regards C.