The onslaught maps have now been added to the regular rotation for the people who bought them so a separate playlist is no longer needed
Hey buddy! I'm glad that gambit1969 was able to answer that one for you. Just a heads up, if you'll get more map pack DLCs like Devastation or Invasion, once the next maps come up, the latest one will have its own playlist and the older ones will be included on the regular rotation. I believe it worked the same before for MW3 and BO2. Hope you enjoy the game!