All DLC has now been integrated into the main game without having to manage downloads.
You can still visit and follow the DLC pages for updates and news, but it is no longer necessary to download the content anymore as the content and story have been woven into the main game for ease of access.
All maps, perks, and bosses that were tied exclusively to the free DLC installation are now available from the start. To experience the full story, is it highly recommended to start a new game, but not necessary.