Of all the items on that list, the ones I really think are fake one way or another are the Volus. Can you imagine the Volus in ME3 multiplayer? The way they look in the trilogy, they couldn't even hold most weapons.
As for Leviathan:
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It does look good, from what I've read, but I won't buy any DLC after the ending fiasco. Whether or not it was supposed to end up in the game or was made up as another attempt to patch up the plot holes doesn't really matter. The ending was a catastrophe and I'm more or less done with the Mass Effect series for the time being, except for the multiplayer.