21 Blast or Stun Mastery

Stun mastery isn't going to up your DPM nearly as much as 21 blast will, especially since we now have spammable blast. I don't even suggest SM until after you've maxed all your energy skills, since its boost is so minimal. Blast is going to help you everywhere, you're really going to want it for Elder Wraiths at 90, where you won't be using Stun Mastery every practically. Stun Mastery will also set you back on Drain, which helps a ton at Himes and NS.