Coming in late on this post. You definately need all the pre-requisites for Enterprise Vault including CDO, along with pre-requisites for Discovery.
If running EV6, you must be on DA SP3, and I reccomend getting the post SP3 hotfixes from support for the export to PST enhancement.
Lastly, did you get a seperate license for that server? You only need a license for DA as the EV services will not need to be run. Once you have a license, ensure the service starts.
LTS