RE: Writer's Lounge
A rubric can be a good idea, since it'll give a set of points on what would-be critics should cover. However, on the flip side, it gives an unneeded rigidity to critiquing, and in some cases it's unwise to have that; critiquing is generally flexible and how it's expressed changes from story to story, person to person.
I don't think I'd be against a demo rubric being drawn up, but at the same time, I wouldn't make it a mandatory thing - somewhat like the Card of the Day questions in the TCG section, i.e. you do not have to go by these questions, but they're good basic guiding points.