Wow, gaining 1 life per white creature every turn? That's a bit good for a 2-drop, and way too powerful for common.

Mass damage prevention doesn't seem like a common ability. What about preventing two damage to three different creatures? By forcing you to prevent it from three creatures, it somewhat restricts when you can use the ability, but it also can be very powerful if you do have enough targets.

Make sure you word it as three target creatures. Also, you could play around with some variations on this. I was just making a quick suggestion.