I think in some cases it could be better than entity, but those are very narrow cases. Notably, when you know your opponent's deck list and what minions they've left. Say, you're going against this c'thun warrior and it's near end of the game and they've like c'thun and doomcaller left, if you put this secret up, you just ruin their win condition, whichever they play. Something like that. It's better than entity against freeze mage because of doomsayer (and any other deck that play doomsayer), it can deny coin from pillager or card draw from acolyte, it can deny gadgetzan for example while entity can't. It can deny like turn 8 Tirion too, so does entity but it's still better with N'Zoth, denying that. I think it's certainly annoying enough but you still don't put it in your deck. Random vaporize can be very annoying and effective too but you still don't put it in your deck.