Tyrannical Curse should deal 15% of the damage to damage linked targets. This works correctly for all powers except the Hellfire Ring DoT which seems to only deal 7.5% of the DoT damage.
https://docs.google.com/spreadsheets/d/1f2TiaX7Ud30Xm-NneWZqhI-hWVmXaQazXu-29KiQLZc/edit?usp=sharing