You want to be able to add two or more domain controllers to the Domain Controller agent configuration.
Release : 15.5, 15.7, 15.8
The Domain Controller Agent fails to manage the mapping of ip addresses with Windows domain user accounts when two or more domain controllers are added to the configuration. Also, unless you disable any additional domain controllers configured above the one, the issue persists.
There is a new DC Agent which has been developed and will be released with 16.0 version. Ref attached symc_dcagent.msi.
This does resolve customer issue and must obtain permission from dev to send to customers previous to GA release.
You can expect the DC agent to run at 100 % cpu when it's performing mapping schedule for approx 30 minutes.