Here’s a thought.
As the base Crit Chance is 5%, how about making Broken Promises lower your current Crit Chance to
1% ~ 4% (variable, 1% would be the cubed value) but add a hindrance to balance things out?
Your healing from all sources is lowered by 40% ~ 60% (variable, 40% would be the cubed value)
Also, making the internal cooldown 1.5 seconds instead of 3 seconds and making it proc only from skill casts and not “on hit” effects like Bastion Revered or Legendary gems like Wreath of Lightning would go a long way in making it more interesting.