Heal is actually pretty good. I do not see a problem with putting in 2 or 3. If you cant get shards this is the next best thing.
I have 2 shards of divinity and 6 shards of gratitude (but only 4 are upgraded), and yet, I often use this card unupgraded in preferance to shards. Reason? heal is great for masteries while shards arn't.
As for empathetic/feral bonds, if you can kill your opponent in 4 turns (ok that is best case scenario, but still), you don't have the time or quanta for a slow card like bonds to pay off. (although in a rainbow a bond does increase the mastery rate significantly)
This card is the ultimate mono-grass speed mastery deck heal, and mine packs 4 of these, having replaced both shards of divinity and jade staff because of thier much better rate of mastery.