I see what you mean, guys. However, remember that this is not a spell. The effect is only triggered if the card is discarded. This means that the opponent cannot play any card and cannot discard any other card (before anything happens). This means that he probably has only few quanta. Also the effect is triggered at the discard time which means just before the pillars generate new quanta.
True, a deck comprising both this card, nightmare and devourer is probably a good denial deck. But this is the strength of the deck and not of the card alone. I don't think, for now, that said combination is better than other good denial combination (devourer/fractal, devourer/earthquake or discord/backhole).
I'll see what the others will say about the card and if everybody (or the majority) say like you guys, I'll change it.