At the risk of recursion (my sig), the problem is not the card itself but the ability granted by it.
Unless thorn carapace + sundial is stronger, then no go.
On that note, perhaps a shield with "If the creature has 5+ health, poison it" would take down phase dragons quickly, while leaving immortals all good
Now that I think about it, that would be an excellent card to see, helps the little critters. Is easily countered by voodoo dolls with damage, swarms, etc.