Maybe if you change the way it works so that it is more useful...
You could always follow purify and make this card give all creatures 1
(purify) marker. Then they would heal for 1 hp per turn until they are poisoned or killed. This would be a nice parallel and make it worth playing the card in ANY situation. That would require quite a cost increase though.
Maybe the card could also have other effects though... Maybe you could target yourself or your opponent and it would hurt fire creatures for 3hp but heal all other creatures? That way you could heal your own creatures OR target your opponent who has a bunch of fire spirits out. Less situational this way.
Maybe it could be a permanent as well that last for x counters or has an upkeep or has a high activation cost?
Just some ideas on how to make it less situational.