According to Microsoft you need to use their built in backup feature or a software that supports AD and VSS which will tell the VM OS that it is going to be backed up.
Unless you do this there might be corruption of the AD Databases according to Microsoft.

ALL THO we've been backing up our AD servers with XOA snapshots (Both normal backup and incremental) and had only 1 issue since we started using XOA in 2016.
Since that issue we also use a guest agent (From Ahsay CBS) that makes a Windows System State backup and Windows System Backup.

More info about that can be found here:

https://wiki.ahsay.com/doku.php?id=public:version_9:client:9447_system_state_backup_vs_system_backup