@nielsenw ...
I am sorry to read that my last response was not helpful to you. You had mentioned the archive, so I wanted to provide you with information on how to request that the links I provided can be restored via request from the Community team.
As far as the rubrics are concerned, when you use a rubric for grading purposes, it takes the points you give for all criteria and provides a total score for the entire assignment. To my knowledge, the rubric does not / cannot automatically calculate an average score. Also, there is nothing documented in these Guides that indicates that averaging scores is a possibility during the rubric creation or grading process:
For example, if a student received the following scores (out of a possible 10 points each) on four criteria: 10, 6, 6, and 4. The total score that Canvas calculates is 26. It does not display an average score of 6.5 (26 / 4 = 6.5). Even if you did use the rubric for grading via the SpeedGrader, you can still manually type in the average score that the student received for the assignment above the rubric when you grade. But, the rubric will still show the total points that you had selected within the rubric for the student. For example, if we continue to use my example with a 40-point assignment...if I click the cells for 10, 6, 6, and 4 when using the rubric for grading via the SpeedGrader, the total will still show 26 points at the bottom of the rubric...even though I could manually type in a different score above that rubric for the student. I could definitely see how this could be confusing for the student, though.
Since I do not know exactly how you have your rubrics set up in your own course, I don't know if trying free-form comments instead of ratings would be an alternative to consider. In my former role as a Canvas administrator, I did not teach courses where I worked, so I didn't have much experience with grading. But, this might be something to look at...not 100% sure, though. Here's the link:
Finally, I thought I'd do a little bit of searching in the Canvas Community to see if I could find any existing Feature Ideas that might closely relate to what you are wanting to do in Canvas. One of my search results was this existing Feature Idea:
Please look it over to see if it might be similar to what you're wanting to see in Canvas. Now, normally I would suggest that you add your own feedback to that Feature Idea and even give it a star rating (which are just a couple of the many ways that Instructure gets feedback from us...the end users). However, earlier this week the Canvas Community team began to lock down all Feature Ideas (temporarily) so that nobody can submit new Feature Ideas, comment on existing Feature Ideas, or give them star ratings. The Community team will be doing some re-org and clean-up of the Feature Ideas, and they will be opening things back up at the beginning of February. In addition, since you are a "New Member" here in the Community, you will need to "rank up" (which is similar to "leveling up" in video games) so that you could submit new Feature Ideas in the future. "Ranking up" in the Community to the next level is pretty easy, FYI. Here are some documents I normally provide folks that are related to what I've just mentioned:
I'm hoping that this additional information will be helpful to you, but I do recognize that it might not be exactly what you are looking for as an immediate solution.
Take care, and be well.