That depends on what you mean by restore a DA user.
You can't restore an entire user (including all references DA needs) by retoring files in a working system, because there are files which contain information about many users. So if you restore a user from yesterday, you'd overwrite any user added today.
We're very happying using sysbk (The DirectAdmin System Backup), because it gives us everything we need if/when we need to restore, but we never just automatically/mindlessly restore. We always look carefully at system files to see what in them needs to be restored.
Why not just do user backups or reseller backups?
Jeff