I'm truly sorry that I read this post a little too late i believe and this may never be replied, but I have to say that I LOVE your idea of making quest, extremely hard quests, to earn cards that are superb, or even nothing at all.
I played elements once, when it was on it's baby steps, when IA3 was the hardest, and when you create something that pretty much has a life of its own you have to come up with challenges that satisfy the need of eveyone.
I think the FG sooner or later will be, I wouldn't say "100% defeteable 24/7", but kind of. Adding a sort of "journey" to defeat an incredibly tough opponent with some kind of reward would give the game much more life than it already has, a story. Perhaps each quest could have a side story into why we are battling that particular hero (I humbly offer my help into making the story).
That way, kind MtG, i wouldn't be just a card game (which isn't), but a tale.
Great Idea, too bad I wasn't around back then.