I've seen some instances of people having issues getting the installer.xml to run. We have had success running this workflow:
Follow this instructions but don't get it to work. I draged the folder to Composer and named the package BitDefender. When running the policy a just get a folder named BitDefender including antivirus_for_mac.pkg and installer.xml in /Users/Shared/
Have I misssed or missunderstood anything?