Because I don't need it. It is a powerful card in the meta but I'm not convinced this deck is where it belongs.
In the XBone meta, he probably doesn't. At least not right now.
I see too many Radkos and Gruul decks on Steam to not run a
Gaea's Revenge. He hits the board running, and they have no way of really interacting with it. With the Graveblade, in several games, I am pretty sure I would have lost due to Act/Sac or a well placed
Ravaging Blaze (or at least would have had to sac them to
Evolutionary Leap).
Because I don't need it. It is a powerful card in the meta but I'm not convinced this deck is where it belongs.
So a single Graveblade instead?
I think Hakeem is running the pair like I suggested earlier, but from the way you've posted the comment I think you're under-valuing Graveblade, especially in this deck. While I don't agree with the choice not to run another easy win con with a singleton Gaea, Graveblade does a lot in this deck and is live a hell of a lot earlier than GR.
Marauder shuts out aggro, counters mill and provides a win con all for 3 mana. If you ask me if I'm running double Marauder or a single Gaea I'm picking the Marauder's every time.
While I like the idea of the Marauder, he doesn't shut down aggro nor counter mill. Aggro just either ignores it (since it can only kill one of their attackers if they are going wide) or kills it (if they can, which is of some use to the pilot of the deck, probably a 2 for 1). Mill just deals with it.
Gaea's Revenge is the hardest card for an opponent to deal with in the current meta, hands down. Graveblade comes down earlier and can do some marvelous things, but for a finisher I'd pick the Revenge any day because it's hard for the opponent to interact with it.
Of course, ask 3 people and you'll get 4 opinions, so run what works well for you.