Originally Posted by
wuberg
I would never run less than four Smallpox, but have tried zero big Pox with reasonable results which is why I don't consider it 100% mandatory. However, I do agree that it's a very powerful card and 1-2 main is pretty sweet. The reason for why I usually prefer Sphere of Resistance and/or Trinisphere over Nether Void is that they drop earlier and effectively do the same job against e.g. Storm. Nether Void does have benefits since it creates a harder lock and can't be destroyed by Abrupt Decay, but it's also trickier to time with your own resources, not to mention that it destroys The Abyss due to the World supertype.
Not running Tabernacle because you have a Nether Spirit main is silly, the same line of argument would prohibit The Abyss as well. Given that the opponent have more creatures than you, she/he will be more severely affected. Furthermore, you can stack the triggers so that you have Nether Spirit in play every second turn and Mishra's Factory is still alive and kicking.
Pithing Needle is indeed great in Pox since it can adress both artifacts and planeswalkers that are otherwise problematic for us. I've been running one main and it seldom disappoints. Oppression is a pretty fun card until you've gotten your hands on Chains. It's a somewhat different effect of course (best in a discard heavy build in my experience), but it wrecks some of the decks that you would want Chains against.