Hi Erika:
Rubrics are perfect for subject areas and assignments where there could room for some degree of subjectivity. The rubric attempts to define beforehand expectations the teacher will have in grading the assignment, and also gives the student some fore knowledge on what will be needed to earn the designated points.
Some students have commented that, while rubrics helped define what was expected, they relied too much on compliance (in order to earn the points) which interefered with their creativity and freedom in expresssing their ideas in the content of their assignment.
In the end, we want to make sure that we are accurately measuring the degree of learning, or degree to which the students met the student learning oiutcomes. Therefore, balancing the various components and using a variety of categories provides the best method to capture the different learning styles, backgrounds, and levels of difficulty for students.
Regards, Barry