What made this tournament particularly interesting for me is the unique way in which these teams presented the old and well-documented RMP comp. It's been around since arena began, playing off of the burst capabilities of the Rogue and Mage mixed with the crowd control combos possible between Sap, Fear, and Polymorph. As one of the older successful comps used in arena play, teams like HON and COM have had years to practice their coordination and control. There's no replacement for the experience of playing thousands of games as a team.
These Rogues had so much experience playing in RMP, in fact, that they're both capable of playing multiple specs within the same team. HARP was en vogue during Season 3, with ShS being our bread and butter for Season 4. As the class has adapted, so have these assassins; they've constantly molded our abilities and talents to match their teammates strengths and weaknesses.
My experience with ShD:
I have not had much personal experience running any sort of Shadow Dance spec in arena play. Running with a build like 17/0/54 Subtlety allows you to pick up most of the key PvP subtlety talents, but forces you to skip many important DPS talents. Without Dual Wield Specialization, Vile Poisons, or Murder, our sustained damage is almost non-existant.
My problem with Shadow Dance is that I am too used to the long-game mentality. On my battlegroup, there are very, very few double or triple DPS teams. It's always a healer and a tanking class with the defensive cooldowns to survive a rushdown. Shadow Dance fails to provide any options for fighting an opponent for more than a few fleeting seconds. Backstab, its main damaging ability while outside of ShD, has a positional requirement that makes it a pain to use. How can you defeat an enemy team when all of your burst comes from one single cooldown?
How ShD is viable:
Thanks to DK, HON's Rogue, I now know the answer. You, with support from your team, simply have to embrace your single opportunity for a kill. How many times have you been foiled when your target had just a few percentage points of life remaining? If you allow your target to recover from a near-death experience as ShD, you have cost yourself the fight. There is simply no way to compete as deep Sub unless you and your teammates have the coordination and burst damage to guarantee a kill. You put all of your eggs into a single basket, and you do everything in your power to ensure that you are not crushed.
The typical strategy that nearly every Rogue employs is to cause your opponent to use all of their defensive cooldowns and PvP trinkets as quickly as possible, and then orchestrate a CC chain on their partners while killing your target in a Cheap Shot -> Kidney Shot combo. The strategy remains much the same for a Shadow Dance Rogue, with an even greater emphasis in nearly every area. You must ensure that your target has no way of escaping your clutches, and you must also guarantee that their teammates will not be able to peel you off of their ally while your precious ShD is active.
If your team is capable of assisting you in setting up this perfect storm of CC and coordination, Shadow Dance becomes the enemy's worst nightmare. Ambush will have a nearly 100% chance to crit, with each crit generating two combo points that will be dropped into a glyphed and talented Eviscerate. When complimented by some minor DPS by your healer and a few instants from your Mage of choice, it is enough burst to bring down any target.
Why Shadow Dance is so scarce:
So why don't we see more Shadow Dance Rogues in arena play? If you're from America, it's simply because there aren't any Rogues playing it. Besides Reckful (who has been championing ShD since day 1) and a handful of others, every Rogue has spec'd Mutilate. I can understand why, the sustained DPS and utility of a Mutilate build vastly overshadow what deep Subtlety can offer.
Without flawless coordination and the ability to draw out your enemies' actions, you'll be unable to succeed using a Shadow Dance build. I had thought about trying it out on my live Rogue, but unfortunately the teams on my BG have already started to adapt to the spec. It's become very popular since the ESL finals, and I've fought against a few teams using it myself. When fighting a ShD team, simply save one important cooldown or CC for when the Rogue enters the dance. Then, CC the Rogue or use your defensive CD. In order for the Ambush to Eviscerate burst combination to be viable, the Rogue must have complete control over their target.
So if your RMP combo is looking for a new twist to liven up your months of practice as Mutilate, feel free to give ShD a try. You can still surprise a large number of opponents, who aren't used to seeing Subtlety anywhere outside of a HaT raiding build. Just be ready for your enemies to start reacting intelligently to your strategy to draw out their cooldowns, as they'll be on guard when you queue against them next time. And unless you have partners that can play with you like second nature, you may want to stay Mutilate spec, where the margin for error is much more forgiving.