Fallout 4 - Far Harbor DLC is biggest DLC yet

According to Gamerant Pete Hines revealed via Twitter that the Far Harbor DLC for Fallout 4
is much bigger than Oblivion's Shivering Isles:

As it happens, one gamer took to Twitter to ask the studio's Vice President of PR and Marketing, Pete Hines, about the magnitude of Fallout 4‘s Far Harbor content, which resulted in the executive saying "it's bigger in size than Shivering Isles," which was The Elder Scrolls 4: Oblivion‘s biggest DLC package.

VG 24/7 also broke the story.