I suggested 3.
Odin 7 
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My main point is that the counterbalancing effect can be circumvented if the opponent is at full health and that having this spell increase maximum health instead of just healing could keep that from happening.
Autokills are tricky to balance because they are supposed to get more expensive for bigger targets.
Having a static high cost like this spell is not necessarily the best idea because it makes it UP vs small targets.
Without a counterbalance, however, it would end up being OP against heavy targets.
The healing effect makes a good counter balance, as long as you can't circumvent it too easily.
I agree that its best to bring cost down somewhere around lightening. However, note that light is NOT meant to be a CC / offense element so it would actually be good to have this slightly UP compared with lightening bolt because that is an aether spell.
If lightning is 1, then this should be about 4.
Seems good to me if this spell is kept as a pure healing counterbalance.
If maximum health boost is used instead it could come down a little more (maybe 3 or 2)
Lastly, if cost is brought down to 3 / 2 AND max health boost is added, it can be used as a sacrifice like mechanic in a pinch (i.e. immediately preceding a miracle) which would make it uniquely flexible amongst CC spells.
