Reporting Filters: Don't Include Approvers that have been removed from the proof approval workflow

As it stands, if an approver is added and subsequently removed from a proof approval workflow, the filters, detailed below, do not seem to work correctly. The first one does not remove these records and the second one seems to remove other records that should be included;

Proof Approval>Approver Decision>Equals>Pending" filter

"Proof Approval>Awaiting Decision=True"

It would be great to tidy this up so that only users who are currently included in the workflow are reported on and all the users who are currently included in the workflow are reported on.