+1 to remove that function
As an alternative, I implemented this function: https://github.com/moodle/moodle/blob/MOODLE_29_STABLE/grade/report/user/externallib.php#L64 to retrieve the gradebook for users.
Note that this function rely in the report API, the information returned is not ready to be treated by external SIS but it's useful if you want to build a visual representation of the user gradebook.
Regards, Juan