Are the Masters obligated to enter this? By this, I'm not saying that I won't enter - I'll probably enter eventually.
As for Devourer decks, I'll probably use a Devourer-Fractal deck. But still, I'd rather use an Aether Mark for that deck.
I propose a change: For Masters, if your deck is 50+% your own element, then you can use a different Mark. Otherwise, for me the Dark/Earth denial deck would not be possible without the Earth Mark, unless I put in Stone Pillars.