How are students supposed to know and remember to check all of these various locations to receive the complete set of feedback provided by their instructors? It is utterly inefficient and defeatist because students don't seem to realize that all this feedback is sitting there waiting for them--and they don't know to look for it.
Now, from a student point of view, I don't want to have to click in so many different places to hunt (perhaps fruitlessly) for feedback that my instructor might or might not have left for me (since there is no indicator signalling the existence of written comments).
The fact that written feedback has been given within the submitted file and within the rubric should be foregrounded--it should be made highly visible to the students checking their grades. That feedback is part of the learning process. It is essential for students to read that feedback in order to improve their work. If they don't know it is there, what is the point?
Don't force users to guess and hunt for feedback. They won't do it. Make it obvious that the feedback has been given by putting some kind of big symbol or message next to the assignment doc (or by displaying the assignment by default so students can see that margin comments etc have been embedded in the file) and also by automatically displaying the rubric WITH the written feedback already visible. Don't make the students click in three hundred different places to get all their feedback for a single assignment. Please.