Is there something specific I have to do? When it shatters I only get the sword heal buff unless I’m misunderstanding the mechanics?
EDIT: I think I figured it out though. Basically requires a skill slot to fake activate it I think but instead of it being used as Chi blade it explodes. Was really hoping it would trigger the effect w/out the cost of a skill ability button. Would the devs kindly consider that…if even w/ a dps loss to let it happen?
You’re misunderstanding how it works - you use Spirit Blade to forge your blade and then ordinarily you can use that ability again while the blade is forged to add more attacks before it shatters. Shattered Hellblade removes the ability to add extra attacks while the blade is forged in return for causing damage based on the amount of chi stored when the blade “shatters” (when the attacks run out).
Just letting the chi expire and give you the Chi Overflow buff doesn’t trigger the hellblade because it’s not supposed to.
Made the same mistake myself a while back 
Few people have asked for the weapon to be rethought:
You might find the following google doc useful for other weapon options, but blade is one that you very much use because you love blade 