This kind of card doesn't fit Hearthstone. In a game like MTG you would actually be able to counter such a spell. I really dislike these kind of destroy cards in Hearthstone. Anti-combo cards shouldn't be instant win against combo decks, they should be like Loatheb in that they stall the combo.
Not sure if a card like that fits in this game and it is such a gamble too. There is a chance that your foe will get their combo pieces before the Warlock uses this card (and let's not forget that Juicy Psychmelon is a thing). I will vote for playable.