Having 2-node cluster, it’s beneficial to have at least 2 AD DC VM’s each located on a separated host. In case of a host failure, you will ensure the AD is up and running. The AD running on a VM also allows you granularly maintain AD and Hyper-V host. Microsoft recommends to run AD either on a Hyper-V VM or/and on a dedicated physical host. It’s not recommended to run Hyper-V role and AD on the same system.
Useful tips for setting up Microsoft Active Directory Domain Controllers
https://social.technet.microsoft.com/Forums/windowsserver/en-US/a65d39f4-798a-432b-896a-543d51ff9038/hyperv-role-and-active-directory-service-in-same-server?forum=winservergen