Great analysis! I'm also confused with Tarsa's artwork, and thought she would be better as a Magic summoner and she definitely overshadows Pyre and Malric. She looks like a great card, but kind of unnecessary.
As for Obsidian, I agree that now Earth will be a lot stronger and less predictable. Maybe her addition will lower the number of Mylor players. Earth is the splinter that I play the least, but maybe it's time for me to invest in some new cards.