Of course, it's important to note that none of these rankings really matter at this point. As Serennia noted in the same blog entry, players only need their teams to be in the top 1000 to qualify for the invitational phase of the tournament. Standings right now are merely observational benchmarks and Aratil's regular updates are nothing more than that -- updates. Although the US Tournament Realms indicate a trend towards the Death Knight/ Paladin/ Warlock team comp, the European side has a fair share of Rogue/ Mage/ Priest teams. That said, the top team in Europe as of this writing is also a DK/Pally/Lock comp that wasn't in the Top 10 last week. In Korea, where teams are still working their way to crack 2000, the most popular comps are the expected RMP with the current top team being a Death Knight/ Paladin/ Hunter. Yep, it's almost the same dominant setup with a Survival Hunter instead of a Warlock.
Some players attribute the dominance of the composition in US Tournament Realms to the absence of quality RMP teams, as RMP is a known counter to it. Others blame the sheer overpoweredness of the Death Knight class and point to the glaring absence of other classes, notably former Arena powerhouses Druids and Warriors. Holy Paladins are extremely viable in Arenas, as well, leading to the current nerfs on the PTR. Whatever the case -- it can be all or none of the above and it's certain that many factors contribute to the phenomenon -- Death Knights have certainly made an impression in the current season and the ongoing tournament.