Options available in User Report "Show Rank" and "Show Percentage" should also be available in Grader Report
I am not sure that this suggestion is a good idea, but I will leave the but open, to see if anyone votes in support of it.
This issue was assigned to me automatically, however I will not be able to work on this issue in the immediate future. In order to create a truer sense of the state of this issue and to allow other developers to have chance to become involved, I am removing myself as the assignee of this issue.
For more information, see http://docs.moodle.org/dev/Changes_to_issue_assignment