I like the universal approach here to grading but I often have trouble with rubrics. It seems that you can earn points on a rubric but still not have an amazing art piece, just as you can have this amazing piece of art that doesn't touch all of the points. I think mutual trust and guidance is crucial in the grading process, as well as the comments and discussions involved.
This is always a great question in art. Rubrics are by far the best way
to go. Ideally, I'd like to use a separate rubric for each assignment
in my course but I have found using one standard rubric makes grading
more efficient for me and more consistent for students.
I assess every major studio assignment the same way.