I get the concept behind the skill costs matching the card themselves, but stone skin used this way will be stronger then the actual stone skin because with this card you only need to draw it and you get heal and purify's healing. More healing=longer games. Longer games=more earth quanta. So, More healing=more earth quanta. More earth quanta=stronger stone skin. More healing=stronger stone skin. Thats why I think that stone skin should get +1 cost compared to regular stone skin. Purify and healing should be alright as it is now because there healing doesn't depend on anything.
P.S. How would the game mechanic work? in the description, obviously put each ability can only be used once, and you may use every ability. (So people don't think you can only use one of them, and only once.) Then also put how the game mechanic behind this card would work.
P.P.S Is this a realistic card to be implemented? Imho no because it has 3 abilities and people already hate sofo. Maybe taking out the stone skin itself would work. New ability for thought to make it more realistic:
Multi-Heal --->heal 20 Hp, a turn later your HP is purified. 3 for the ability upped. Cost of it should be around 6
to make it somewhat hard to fractal. Fractaling something with heal might not be a good idea. Maybe even 7, but raise attack to two and HP to 4. But I would be content with 6 simply because of the low attack and low HP anyway +expensive ability. Heck, maybe with 6 you could raise attack to two and HP to 4 anyway and it would still be balenced. I like this type of idea simply because purify just isnt used much outside of arena decks.