To the best of my knowledge, Moodle does not have content analysis capability, and what you are talking about may not exist at a level that is useful for instructors. I lean more toward your later comments. Assessment has to be tailored to the needs of the students and the instructors. Instructors might consider a combination of online objective questions, which can easily be autograded, and longer essays/reports, which can be done either individually or in groups. I find that the combination of both types of assessments works well, and allows instructors to get a good picture of how much students actually know.
One strategy one of our faculty uses is to get students to come up with objective questions about the material and post to the forum. That really shows whether or not they learned, produces lively discussion, and seeds the instructor's question bank. Talk about bang for you buck!
Good luck.