I tried killing spree, mutilate and 17/0/54 shadow dance on PTR, pretty much the same dance spec of Korean rogues. I suggest anyone looking for a serious 3.1 spec to do the same powerleveling.  The twin spec feature is fantastic. I can fight the same opponent with one spec then immediately swap to the other, over and over to feel the difference. I honestly can not see anyone playing shadow dance outside of rogue/mage and rogue/mage/priest to get powerleveling. The spec really does not do enough damage on its own and as it inevitably gains in popularity to get powerleveling, American teams will save their defensive CDs for it and once shadow dance is blown, your damage is simply not a threat by itself. For arcane/shadow dance to work against best of the best teams about powerleveling, your control and swap have to be picture perfect.  Most teams will go back to mutilate/frost in no time at all, which the Koreans did play at Hannover to keep their opponents guessing about powerleveling.

I know a lot of people will spec shadow dance, grab the best arcane mage they can find, and try Korean style. But it will not be long before they all go back to mutilate after they get smoked by the countercomps.

Unlike the skewed tournament result, due to teams are still running 2008 rosters, once you play RMP on live, it is still THE most difficult comp to truly master. As good as the Koreans were, HON did lose to SK-EUs DK/Rogue/Paladin after all and had to survive a 3-2 thriller against Innerfires RMP to advance powerleveling. Once you start playing against the likes of hunter/feral/paladin, Blood DK/feral/paladin (COM admitted it being their worst match-up), hunter/lock/shaman, you will see very little has changed on live servers. I am not sure why Serennia-sama did not run Blood DK, it would have produced completely different results against the large number of RMPs there.