Double-posting much? 
Is part of the singleton Warrior deck that is actually supposed to be beatable by Warlock… probably not much else. Plague Death Knight could also do things, but it’s not really playable on the ladder, and the reduced Plague package seems to be insufficient and is usually too late for some reason (Warrior has the hidden ability of making Helya one of the last cards in the deck) — I think I might have had better results with DH than with this against those kinds of Warrior decks.
The way I see it [1], [2], the problem is not Zilliax, but Deepminer Brann himself: it’s a card that can be played with anything, be it Odyn, Tentacles, Boom-Boom-lord and whatnot — anything goes and is OP, and if it happens, usually at 6 mana, the card in question instantly makes Warrior unbeatable, untouchable, unstoppable and destroys the opponent’s hero, at least morally (yep, self-repetition again). I’ve already suggested (see the references above) nerfing it at least to 15 mana, but so far it’s been running rampant.