In a proxy chaining deployment it is possible to have the child proxy forward dynamic categorization requests through upstream proxies. See SGOS Administration Guide for more information.
If DNS is not configured on the child ProxySG you will see that the DRTR health check will fail, even though WEBPULSE and BCWF is functioning correctly.
In order to avoid having DRTR health checks fail the child proxy needs to be able to resolve sp.cwfservice.net for SGOS 6.5 and webpulse.es.bluecoat.com for SGOS 6.6.
The preferred solution would be to allow DNS forwarding so that the DNS resolution could succeed. This could be limited to only work for sp.cwfservice.net
An alternative solution might be to set DNS proxy on the parent ProxySG.