How many metrics are you collecting in the large vC Ops installation? How is the appliance configured with respect to cpu/mem and Disk IOPs capability of the datastores it's running upon.
Go in to the Custom UI, go to support > info, then open the support dashboard and see if any red flags/alarms have been raised.
Try configuring the widget to show Resource Kinds > Host System instead of working off the datacenter resource.. it'll open up the resources you're analyzing.