I would use Cryptolith Rite instead of skyshroud elf for avoiding blood moon effects because it makes all creatures into mana dorks and also just costs 1G. Other than that I think the deck looks pretty much tuned and having not played with it I can't really suggest more changes. Other than that, I can imagine that Humility, Torpor Orb and Cursed Totem are problematic to deal with. I have the same problem in creature based combo decks - either give up slots for removal that is not packed on a creature, or be vulnerable to exactly those cards.

@Winterblast: Thanks for taking the time to take a look at the deck. Regarding your comments, I talked about Cryptolith Rite in the 'single card discussion' section of the deck description. Briefly, the card is okay but not good enough to make the cut. Creatures with summoning sickness can't tap for mana, so contrary to Earthcraft, it probably won't allow us to produce degenerate mana during the same turn you cast CRite. Also, Earthcraft usually produces more than one mana because of the mana doublers in the deck (e.g., Wild Growth) and we need untapped creatures for earthcraft and Chord of Calling.

I should have explained the role of Skyshroud Elf more in depth. It's not there just to avoid blood moon-type effects; it can do that, of course, but its primary role is to convert mana from cards like Gaea's Cradle, Earthcraft, etc., into mana we can use to cast our general and win cons. That's the reason I wrote that skyshroud should not be meta-dependent--I'm pretty confident that it's a must for this deck.

As you mentioned, however, there is a couple of enchantments and artifacts that can be somewhat problematic for creature-based decks (Humility is a very good example, so thanks for bringing that to my attention.) I've thought about that and the existence of those cards is one of the reason we have cards like Nature's Claim and Beast Within. Interestingly, none of the cards you mentioned will affect the the Purphoros storm kill as long as you can storm under such conditions, which is not that hard tbh. The really problematic cards are the ones that don't allow us to keep a bunch of tiny creatures on the board (e.g., Elesh Norn, Grand Cenobite, Spreading Plague). But then again, we have multiple ways of answering those cards and win the game.

You are missing the strongest combo Marath has to offer, Earthcraft+Doubling Season effects. Other than that pretty good list

@Entrei: I was just making changes to another deck and saw your comment. Thanks for the suggestion. I talked about Doubling Season and other counter/token doublers in the single card discussion section of the deck description (it's getting pretty long now, so you might have missed it.) As strange as it sounds, I don't think those counter/token doublers belong to competitive Marath lists. As you mentioned, they can combo with Marath + Earthcraft or Mana Echoes but there are several reasons why they are not good enough to make the cut. First, they are three card combos, which means that they are hard to put together, easy to disrupt, and expensive mana-wise. Second, they require us to find and resolve two enchantments, and the deck is not particularly good at finding those. Of course, we could add something like Academy Rector but rector for a card that does not impact the board immediately sounds bad. Third, those combos require setting up the board to make it work--that is, you will likely need multiple turns before going off (casting a combo piece during one turn and the remaining combo pieces during the next turn). Chances are that if you can make all three cards work in a single turn, you can also win via any other win con, and there are better win cons... I know those cards seem to be a good fit to Marath lists but honestly, it turns out Marath doesn't need them.