Paul,
What's the Vault Stores sharing level? If you are sharing at the Vault Store Group level, you need to restore everything; if you are sharing at the Vault Store level, you could restore the mailbox partitions and remove the Vault Store information related to the Journal archives from the Directory database. Of course, I am assuming that the mailbox archives and journal archives are in separates vault stores. Otherwise, the Storage Service will not start in the DR.
If you restore the VMs in a different subnet, you just need to update the local hosts file in the EV server and SQL to reflect the correct IPs and make sure both servers can communicate with the DCs for authentication, etc. Also, remember to disable the archiving tasks in the DR.