I've toyed with it before...
permanent, acts like sundial (lasts 1 turn)
Name: Interrupt
Cost: 4
Ability: All cards being played have a 50% chance of failing.
Note: Affects yourself as well.
So, in the new version:
Healing Spells = ('Siphon Life','Heal','Flash of Light') Any others?
Is using Epiphany considered a healing spell?