The unique affix only applies to the explosion itself (including the Arcane Orbit rune), second blast occurs with a very brief delay, at the same location. It does not affect the periodic damage and damage done as Orbs fly.
Stats (Level 8)Edit
“Yet another item allegedly taken from Vyr’s armory after his demise. It uses the inherent instability of Arcane power to enhance its destructive efficiency.” — High Councilor Valthek’s Compendium of Exotic Weaponry