The problems are two: it is conditional because it need another card to function. (it is actually double conditional because it also require that the opponent have cards in his hand to discard).
Second it says 'discard', not sacrifice, which would have made it better for us that run pox effects. Also: even if your opponent have no cards in hand he will have lands and creatures to sacrifice.

Third: the effect is not only random for you, but the opponent have occasionally opportunity to choose what you well get; Liliana and the pox effects leave it to him to decide what to discard.

Thus the card is triple crap, but it would all be OK if the card was renamed: "Goblin Necromancers revenge"