As rubrics are created and assigned to activities, both teachers and students would expect that a link to the rubric be located in close proximity to the activity description - which is where teachers would most likely include instructions for the activity and reference the rubric provided. There has been thought and effort placed in providing options for the activity description to be displayed below the activity link on the main course page as well as displayed when the activity is chosen. A rubric is valuable companion to any description in that it provides instruction and a framework for the activity.
I would value a standard implementation where the rubric associated with the activity can be linked (by default if the preview is allowed?) directly below the activity description content.
Currently, the availability of the assigned rubric to the student is dependent upon having the Navigation block appear on this page type. If this block does not display, the rubric is inaccessible. Also, the teacher view show the rubric in a different location (Settings -> Assignment administration -> Advanced grading). Instructors may likely provide inaccurate instructions to students on where to find the rubric since they would not think to view as student role AND look in the Navigation block when they find rubrics in the settings block.
If there is a link for the teachers to the rubric in the same manner explained above that would help with some navigation consistency between roles as well.