Its the Elementals ability to return to the battlefield from exile that makes it really interesting, though
While, yes, Dictate may be one more mana than the Furnace, it seems well worth it to flash it in during someone elses combat step, killing off an unsuspecting opponent
You see, you only lose the life if you actually draw the card and don't replace it
As long as you're in a format where you can play Fetchlands to fuel your graveyard, it's essentially an upgraded Llanowar Elves that can heal you and damage your opponents without having to go through their creatures
It will get a few that you might not think of, such as Canopy Vista, Irrigated Farmland, Prairie Stream, and Scattered Groves
My personal take