For my environment having a domain filter to exclude the trusted domain also removed it from the dashboard system health. Assuming you don't need that domain as an option for anything View related, have a look at the vdmadmin command and configuring a domain filter, http://pubs.vmware.com/view-51/topic/com.vmware.view.administration.doc/GUID-582DCABE-A944-4808-9708-E415A0ACFF7F.html.
Jeremy Ey