It's basically a combination of handlock and zoo where you get a strong early lead with minions, but you have moltens and faceless+leeroy as a finisher.
I think it's actually viable at the moment, but it's just not consistent enough yet.
While most people were putting down the voidcaller as situational and mediocre, when I asked Gaara in chat about it, he said it was broken. And seeing this midrange style actually have some serious potency, I couldn't agree more.
It'll push midrange lock over the edge with cards like abusive seargent/dwarf+nerubian egg, as well as abusive + voidcaller to kill a yeti and bring out a doomguard.
Basically, it'll make for a very powerful deathrattle-trade-up deck.