Modified by Edit
Arcane specialization ability
Frost specialization ability
This spell sees a lot of use in PvP. Instant spells are impossible to interrupt, and spells and abilities that slow casting time have no effect. The only way to stop an instant is to silence the caster.
Instants can be cast on the move, as in kiting, or to chase or escape another player. Fire Blast must be cast while facing the target, but it is possible to jump, turn back to cast, then turn forward again before landing. The target only needs to be within the 180 degree arc in front of the caster.
A common technique to achieve burst damage is to cast Fire Blast right at the tail end of a long cast spell, such as Fireball or Frostbolt. After the long cast spell is finished, the global cooldown is also finished, and both spells will land almost simultaneously. Use the global cooldown time from the instant Fire Blast to move and gain range before casting again.