After trying Arcane for the first few pulls, I agree that Fire is probably the best for this fight. AoE on the adds in the 3rd phase is pretty important. However, I'm unsure if running with PoM or Scorch would be better in terms of burning down the Sparks. I have a little bit of trouble getting the last set just because I feel the cast time of Fireball is a little long. I used Scorch almost exclusively on the Elementium Bolt on Deathwing and found that to be better (more spells, more chance to crit, more chance to proc a Pyroblast!).