How about this instead:
It' All Mine! (Immediate Interrupt; recharge 5-6)
Close Burst 20
Trigger: The Lord of Envy is in the area of a close or area power with the Healing keyword.
Target: The originator of the triggering power
Attack: +28 vs Will
Hit: The triggering power has no effect and the Lord of Envy heals 216 hit points.