The Control Warlock archetype wasextremely powerful in the Year of the Raven. But after the rotation happened, it lost some of its most essential elements, such as Carnivorous Cube and Voidlord.
However, the concept of the Control Warlock isn't lost entirely this time; it has simply changed to a fatigue archetype.
You can use cards like Augmented Elekk and Plot Twist to create many copies of cards in your deck, and eventually, you can turn this into a draw engine that will never make your deck go into fatigue stage, unlike your opponents.
Then, you can use a new legendary Arch-Villain Rafaam and transform all of your cards into legendaries, which would completely devastate your opponents and prompt them to concede.
So it looks like Warlock has more chances to survive than ever before.