Technically what i provided was a diff file. I couldn't get the patch export for git working on Moodlerooms private repo the way i wanted.
The diff is of 2 files.
The simplest process would be to edit each of those files and read through the diff file and add the lines of code that say add. I didn't actually remove anything from the code (even if the diff says I did).
My concern with this is that it would be a direct hack of core. I would instead recommend copying the grade/gaming/form/rubric directory and renaming rubric to something else. Then apply the changes to that. This way you could upgrade the Moodle rubric without fear of these changes impacting you. I think the posts above give a clear indication that were Moodle HQ to consider this feature they would probably do it in a more involved way to provide more flexibility to the rubric than just this simple request. This to me means that what I did would most likely not get in to Moodle HQ directly, it would be modified.
Attached is a copy of my rubric directory redone on stock Moodle 2.5.1