Usually high-cost creatures should be used with mono/duo decks, and low cost with rainbow decks. It looks like it will be quite a few turn before you can play the first dragon. You have next to no defense and no shielding or weaponry. You said this deck produced a rare "wow", yes? Was this against another upgraded deck?
Anyways, I would add a couple weapons and shields to replace a dragons of that element. You were on the right track with improved miracle, now maybe add some vampire daggers and permafrost shields?