I don't find the fault in the rubric idea but in the writing of it in the manner you describe. I would rather the top grade say something along the lines of "Thoroughly describes the project and gives many examples that support the findings" or something along those lines. Something that allows both the teacher AND the student some room to make an evaluation based on the student's individual abilities yet is still objective enough for grading purposes.
Breakaway, I agree with what you say about the style of the writing. In my experience though when a teacher is required to give a rubric it needs to be specific and detail exactly what is required to get each number grade for each category. However, if you give more broad statements like what you've described, it is called criterion marking. The difference is just what you described - criteria allow teachers the flexibility to differentiate between 13 ok sentences and 13 super sentences describing the topic.
I love to use criteria, but do not like using rubric, mainly because it almost forces kids to do more than the minimum just to ensure that they get the top grades. However, most of the parents at my school can not deal with the ambiguity of criteria and pressure teachers for rubrics instead. (I think it is a control factor - they then can control exactly what their child produced and know what grade they will receive before handing it in.)
I could go on and on about this, since it is one of my frustrations as a teacher trying to teach critical thinking skills and scientific reasoning, but will spare you all my rantings and stop here.
