All three are good, but I'd recommend Sunsinger and Stormcaller the most. For Vault of Glass: Sunsinger. The ability to stay alive as well as do high level boss damage is really good in every encounter here. For Crota's End: Stormcaller. There are no DPS phases in this raid, but tons of adds. Thus, Stormtrance is brilliant here and the only thing you should run. For King's Fall: Sunsinger or Stormcaller: There are sections (Golgoroth) where Stormcaller is incredibly useful, and Sunsinger is great to do boss damage and prevent wipes. For Wrath of the Machine: All three: Sunsinger is best at Vosik to stay alive, Stormcaller is practically a necessity at the Siege Engine and Voidwalker is good for quick damage at the Aksis Challenge. Don't use Sunsinger unless you're really unconfident at Aksis. Self resurrection messes up Empowerments.