Broken Synergy (Witch, Blasphemy, Hexblast, Whispers of Doom)

I have combined the following skills together.
Blasphemy (apply curses in an area around the player) - Support Gems of Despair and Enfeeble (2 curses)
Hexblast (Detonate a curse on every enemy in an area) - Support Gem Echo (cause the skill to echo a 2nd time after a short delay)
Passive Skill: Whispers of Doom (you can apply a 2nd curse)

Expected Result: Casting Hexblast on an area will cause 2 explosions, once for the initial cast, once for the echo. Hexblast can continue to be cast as 2 curses are applied on the enemy, so simultanious explosions can occur

Actual Result: Hexblast does not echo, only 1 explosion occurs per hexblast cast

Recommendation: Change Hexblast to detonate all curses on an enemy. Fix echo support gem to allow it to double cast for a 2nd pair of explosions