I worked on this rubric for years, tweaking the points and categories until it was just right. Firstly, this rubric is helpful because gives more weight things that are more important: how well the writer synthesized various information with their own analysis, how well they used MLA format, and what quality of information did they find. It also judges papers on the clarity of their overall organization, paragraphing (unity and coherence) and "concise, lively prose."
I also like this rubric because it gives me space to write a few words or short sentences in each category. I found that I was doing more writing on the rubric and less line-by-line correcting on their individual papers, saving me *lots* of time.
The points are calibrated to add up to a typical grade for each category. For example, a paper receiving all "above averages" would count as a 94, and paper scored "satisfactory" in all categories would come out as an 85. In my experience, this rubric is fairly "accurate."
You have a lot of flexibility in how to grade the MLA format section. (By the way, feel free to customize this to APA, Chicago, etc.) The range of points in that category goes all the way down to 5, so depending on the kinds of errors made, you can assign penalties accordingly. (Comma errors versus paraphrasing errors for example).
Lastly, there are two rubrics per page to save paper. :D
This rubric would be useful for Middle and High School Level students.