WORKAROUND:
Install a separate Enterprise Reporter server instance in the DMZ to collect data.
There are two enhancements related to Enterprise Reporter supporting a DMZ environment that were created for including this functionality in a future release of Enterprise Reporter:
Enhancement ID # 1905: System: Ability to collect and report on information across a non-trusted DMZ domain.
Enhancement ID # 337: System: Support for untrusted domain collection with node in untrusted domain - DMZ.