Because the way their are now with a limit of one barley anyone will use it unless their back into a corner especially classes like Force, Techer or Summoners with low defense. Soloing is impossible when it take a total of four hits to kill you.

Dark blasts are victims of power creep, so they aren't very useful anymore, if they ever were. Also, soloing what is impossible?

DB is good for Covert Ops (Divide) but that's all I can think I can use it for.. maybe if you're about to die so it's like a "will" xd?