Activation delay of curse auras with Windscream unique boots

Unable to proc Hexblast multiple times with Spell Echo or Unleash on enemies within Blasphemy curse aura. Seems to be a delay in reapplying the curse that causes repeated activations of Hexblast to miss. Windscream unique boots specifies curses have no activation delay, I believe this should apply to Curse auras and Cursed grounds as well.