Riot, how about this for Leblanc?
Sigil of Malice: Damage reduced.
Distortion: Deals increased damage to enemies recently damaged by Sigil of Malice. Killing an enemy champion with Distortion extends the duration of all active Distortion: Returns.
You'd shift some of the overwhelming power from her passive back into a conditional effect on Distortion and give her more options (leeway on when and whether to return with Distortion) to trick her opponents.