Overcharged Amalgam is interesting but I don't know how regularly I want to pass turn with 4 mana open. It depends entirely on the deck. In my Varina deck, I seldom want to leave 4 mana open for a counter spell. Now if my
Sidisi, Brood Tyrant were still zombie tribal it would wreck face in it as that decks counter magic is on creatures (
Frilled Mystic and
Mystic Snake). However, if you're playing
Rooftop Storm the card is probably a sure thing regardless.
Archghoul of Thraben is the card I'm most excited for so far. It definitely is heading into my Varina deck, and may even find its way into my Sidisi deck even though it isn't full on zombie tribal anymore (the way it churns out tokens them dying happens often, even if the top card has little chance of being a zombie it can still go to the graveyard and trigger Sidisi if it's a creature).
Geralf, Visionary Stitcher is interesting. The flying buff is at a better rate than
Hordewing Skaab which is attractive though the second ability is vastly different and not one I really see using much in any of my current decks. I can see a case for putting either (or both) in a deck. To some it will likely come down to whether or not they want to keep their zombie tribal "pureblooded" zombie. For me, it'll come down to preferring the 2U casting cost over the 4U for the main reason I'm playing one (the flying buff).
I am excited to see Exploit returning and am happy to see that they are finishing the land cycle.