21 Blast or Stun Mastery

I think that getting Blast to 21 would be much more useful, for, not only does it hit an extra target, but it does significantly more damage. Like others before me have said, Stun Mastery requires using DU or BSB to activate the initial stun, and the it only adds 60% damage onto your attack when maxed. Even if a mob of 4 wasn't present, the extra damage from Blast should prove better than Stun Mastery's.

Exactly, here we have sense. The only real use for SM where you'll get its full potential is when you're 100% stunning the Goby houses. Y'know how much that adds per hit on average? 36%. Not worth it before energy. Anyone who says you could save yourself an entire attack with SM, you're only saving about half a second. You're going to save more time with blast while you're killing the gobies.