Seems like it's the wrong class for a card like this. While the effect is powerful, especially considering that a lot of deathrattle minions will leave the meta, it's also extremely costly. Twisting Nether will probably for the most part be a better option since the card draw aspect isn't all that relevant in a class that has access to an almost unlimited amount of card draw.
Not sure why you want to draw so many cards as a warlock. Seems too situational, especially when control oriented warlocks tend to have pretty full hands from tapping often. Would risk overdrawing or fatiguing too fast.