Hi Randall,
Grading rubrics are good because they tend to limit the subjectivity in grading. Rubrics can vary in their effectiveness. If we are trying to get critical thinking skills reinforced, a rubric that only measures mechanics is probably going to fall short. I tend to feel instructor made rubrics are better than those provided by professional or textbook publishers, but not always. For me, a good rubric will measure the desired learning accurately and be aligned with my studentent learning outcomes (SLO's).
Barry Westling