Unfortunately, it seems to not be buyable on Steam anymore: https://store.steampowered.com/app/206177/Rocksmith__Avenged_Sevenfold_3Song_Pack/
I have not found any explanation for why they would remove it.
I have RS 2014 for Windows and wanted to download the official Avenged Sevenfold DLC (containing Afterlife, Best and The Harlot and Nightmare). On this site it is listed as an official DLC. However when I find it on Steam, it is not available for download. Also, the original Rocksmith game is no longer available on Steam.
Is there any way to obtain these DLCs today?