I actually wouldn't be surprised at all to see burn doing well at the GP. It's very cheap and can steal wins against any deck. Chill is really good but very narrow. Misstep and spell snare are great, assuming you are hard casting misstep. Discard is great too as it typically saves you at least 6 damage. But you need to kill them quick enough so they don't just draw enough damage to win afterwards.
I find that the best way to battle show and tell or natural order are to never let them resolve. Between discard and counters it isn't incredibly hard, but a progenitus in play is pretty much unbeatable. Jace can answer Emrakul if you get him in fast, which usually involves slowing them down for at least 4 turns. The midrange creatures in those decks see the bigger concern IMO.

