That rubric sounds really good--this is what an A paper does and so on. Right now I have a 5x6 grid for a total of 30 points. But it's difficult for me to justify each and every box. It's a feeling not a measurement, and boy the students know it. They're like, "But why?" And when I'm grading, I decide on the grade the paper deserves and then tick the boxes, otherwise exactly like you say, they lose all their marks on the unimportant stuff and I have to re-do it anyway.