The ERGA (Education Research Group Adelaide) website includes a range of sample rubrics which might provide some pointers to better rubric design.
References on rubrics
Allen, D and Tanner, K (2006) Rubrics: Tools for Making Learning Goals and Evaluation
Criteria Explicit for Both Teachers and Learners, CBE-Life Sciences Education Vol. 5, 197-203, Retrieved 23/7/09 from http://www.lifescied.org/cgi/content/short/5/3/197
Barron, Keller, Use of rubrics in online assessment (2005) Evaluations and Assessment Conference, 24-25 November, 2003 / 14p., The University of South Australia http://www.unisa.edu.au/evaluations/Full-papers/BaronFull.doc
Moskal, Barbara M. (2000). Scoring rubrics: what, when and how?. Practical Assessment, Research & Evaluation, 7(3). Retrieved July 23, 2009 from http://PAREonline.net/getvn.asp?v=7&n=3 .
Muirhead, B. (2002). "Effective Online Assessment Strategies for Today's Colleges & Universities." in B Muirhead (2005) A Distance Education Reader: Insights for Teachers and Students ISSN 1550-6908 Retrieved from http://www.itdl.org/DistEdReader.pdf#page=103