Beautiful rubric, Tara! I really liked how you constructed it in Excel - brilliant!
I like how the rubric serves as a teaching tool as well as an assessment tool. It's always great to inject opportunities to educate students (or instructors) about expectations. And I particularly like how you're going to use this rubric throughout the program. For my rubric, I hope to do the same thing and I like the consistency of that, as students will gain more and more familiarity with the way they are assessed and build on their skill development each year.
My only concern is that the weighting for mechanics is so high. Really only 25% is for the subject material. I know you intentionally want to focus on mechanics in first year. However, I think some students may think that there is too heavy of an emphasis on writing skills and they may discount the importance of the subject material. Just something to ponder. :)