Voodoo Dolls... As much as I like the idea of a 16 health (Holy Lightproof) Darkness creature, I have never been able to make them as effective as I would like.
Probably because, like a number of the scorpions, they require a second card to make them useful. Generally using up 12 card slots in a deck, and creating opportunities for the opponent to gain card advantage with freeze, reverse time, etc., and generally slowing things down.
Playstyle-wise, I prefer either more aggression or more control. Dolls seem inherently reactive, and while they can delay enemy threats, they don't remove them. I am still looking for a deck that feels strong with them in it.
On the other hand I love quanta control. I agree entirely with plastiques observation about high quanta opponents. Earthquakes I use in almost all of my serious decks that use earth (unless I am expecting speed rainbows/cremation). The Devourer/Earthquake combo is one of my favorites, and I think that both Devourer/Earthquake and Devourer/Discord are strong options against any of the opponents that are building decks under war rules, with the possible exception of Underworld and Fire.
I haven't found that I require a full 6 earthquakes in these kinds of decks. Usually 4 is enough to get one in time to play it early. Generally the slowdown from early pillar loss is enough to swing the game. I don't usually feel that I need to destroy every pillar/pend played for the entire game. I'd like to hear other folks' experience with it though.
Also worth noting, that if I was fighting Darkness, I would always assume they were going to try to use Devourers and Steal. I would try to tweak my anti-Darkness decks accordingly. Thinking about Nova, or a couple quantum pillars, to try to blunt their effectiveness. Also thinking about permanents, I'd expect to see anything important to have Enchant Artifact on it, or for people to push the creatures and spells, and not rely on permanents for key deck components.
A handful of Novas are easy to splash in for any opponent, and gives them fast and easy access to Holy Light, Reflective Shield (stealproof, and saves the player from Drain Life), etc., and a single Nova mitigates 12 turns of quanta drain from a Devourer. Just some things to think about.