ranged or ranged area attacks provoke OA's
Melee and close attacks do not.
Dragon's breath is a Close Blast 3. no OA
So far, all blasts are close blast X. No OA (doesn't mean there can't be some power that is a ranged blast)
Bursts can be either Close (centered on the caster) Bursts, and thus no OA, or Ranged Bursts (Burst X within Y), and thus provoke OA's.