Deathrattle Rogue is a fairly old archetype that has been mostly on the fringes of the meta. Stuff like Tomb Pillager, Undercity Huckster, and Roll the Bones had been added to the class in an effort to promote the deck style. It only really saw some play with the Jade package, but even then it was never in the top tier of the meta.
The Boomsday Project might have been the expansion that finally brings the archetype to the top of the meta. It got cards like Necrium Blade which when the weapon is destroyed will trigger a random deathrattle on a friendly minion. It also got Necrium Vial which will trigger a friendly minion’s Deathrattle twice! Those two cards give the deck some pretty big power, and with Carnivorous Cube in the mix the deck stands a chance at seeing some real play.