Thanks for your response. We're trying to setup a global role for auditors as well.
I've set everything to prohibit, bar two items under the Activity: Assignment
The View Assignment is allowed and the Grade Assignment is set to allow.
Reason being, unless that's set to allow, the user can't view students submissions.
They're only interested in viewing the student submissions. Disabling that, only allows
them to see that Assignment and grades, but not the student submissions.
The problem lies in the fact that the option to grade them is left opened to them, which isn't ideal.