This is the deck I've been playing in expedition for the last few weeks (with only minor changes), and I just got rank 1 with it. My record with the deck since I started keeping track is 94-20 (42-10 at the end of last month, 52-10 this month). I would play this in the ECQ next weekend if I wasn't busy traveling then. The deck is not easy to play optimally, but I recommend it to anyone who likes decision-heavy control decks. I probably won't play it much more myself because I'm a little bored with it, but I had fun with it for the first 100 games or so.
Some notes on the deck:
1) Credit to mgallop for the name (Superior Xenan); the idea is that this deck plays a ridiculous number of 0/x units (0/1, 0/2, 0/3, 0/4 are all important 4-ofs) and thus is the natural enemy of Inferiority Complex (curse played by Temple Shihan that grants Reckless). If you dislike the name, you can just call it Xenan Control.
2) On the other hand, you should not think of this deck as "Big Xenan" or "Xenan Cultists". The units aren't big and this is not at all a midrange deck (unlike most things called Big Xenan). And although cultist synergies certainly exist, they really aren't a central part of the deck, just a few synergies from individual cards. The deck isn't playing Zhen-Zu (which would be awful here) and isn't trying to maximize on value from Ark of Sol or Karvet exalted. This is an Incarnus control deck that is playing some T cards because they are individually powerful.
3) I started out with 3 Nahid's Faithfuls and 2 Shadowlands Guides, then trimmed them a little more after playing with them a bunch. The Faithful/Guide package is certainly powerful and it's possible that there's a different build of this deck that wants 4/3 or 4/4 of them, but I found that they were among my worst cards in control matchups and I've been doing fine without them against proactive decks.
4) When looking at starting hands, you usually want a hand with a turn 2 play. This can mean T1 Faithful -> T2 Ark if you are on the play, or T1 Stone T2 Devour, but more often it means High Prophet or Nahid's Choice making 2 1/1s (you should always make 2 1/1s on turn 2; the other mode is for hitting sites/sweepers later on in control matchups). If you have the choice between High Prophet and Nahid's Choice and have a 3rd power in hand, it is usually correct to play Choice on T2 and then Prophet + attack + Ark of Sol on T3.
5) Don't just snap Worthy Cause off on the first target; it is an incredibly powerful removal spell and you can usually get a lot of value from it. Against mastery decks it is a great fast response when they put Persuader or Jack's Knife on Cozin or Whelp or Varret, while against Ely it is your only maindeck answer to Sodi. It is also your only maindeck answer to Incarnus, but you can often let Incarnus hit you a couple times first before actually killing it.
6) Using the market is fairly straightforward. First you have three removal spells - Malediction is situationally great against a number of decks (though less good in cases where you have a High Prophet out), Edict is a very efficient card against the proactive T/J decks (and is a cheap Sodi answer), Fell Ritual is a catch-all that hits Incarnus and Eclipse Dragon in particular. Then there is Temple - this can function as a removal spell (or two), but usually you are just getting it against control decks (especially the mirror, where Scare kills a bunch of units). And finally there is Ark - I've gotten this from market a few times when desperate for power or when it enabled lethal with Karvet exalted, but mostly this is just to smooth out your early game. You aren't the best Ark deck, but it's still great (much better than market power would be, for instance).
7) Wingbrewer is one of the most important cards in the deck - it isn't your only way to draw cards, but it is the most powerful if not stopped. You should view it as a 5-drop and only play it as a 3-drop if you are stuck on power and don't have other good things to do. I'm playing Wingbrewer maindeck instead of Temple because it is far better in matchups like Combrei and Elysian, while still being good against control. You don't need a board to run Wingbrewer out and have it be good, while there are a lot of board states where Temple is just a Xenan Augury that gains a few more life (because it dies immediately). If you want to run maindeck Temples, I think you need to run more Faithfuls/Guides and I'm not sure it is worth it.
8) Incarnus is arguably the strongest card in the format, and there's no reason not to run it here. One thing to remember is that there's no rush to play it on turn 4 - you often want to play Eager Offering first for instance (unless you are concerned about opposing Temples), or get Wingbrewer going if you have 5 power.
9) Karvet isn't really your "finisher", just a powerful tool to catch up on board. If the opponent doesn't have removal then they usually can't really attack profitably into Karvet, and even if they do have removal you got a free 1/1 chump blocker to help survive another turn. Karvet getting removed also sets up your real endgame, which is Vara. Vara will chain together all the Karvets in your void and let you play an Incarnus/Smuggler/Wingbrewer at the end of the chain; this is usually impossible to beat without a sweeper, and you can usually just outgrind decks with sweepers. We are playing 2 maindeck Varas instead of just putting one in the market because that market slot is very valuable and you have lots of card draw to find a Vara anyway. (You also don't actually need Vara to win most games - more often you just get ridiculously far ahead with a Wingbrewer or something.)
10) One of the more controversial aspects of this build is probably the lack of emblems. The issue with emblems here is that you are an incredibly power-hungry deck with all the Wingbrewers, Incarnuses, and other card draw, and you don't flood out easily at all. Yes, very occasionally you have a game where you run out of card draw, flood out, and wish you had an emblem to replace power 9 or 10 with a 2/2 that would let you survive a turn longer. But if you add emblems, then there will be a bunch of games where they just cost you 1-2 life for no benefit, and that can also mean the difference between winning and losing very easily. Basically emblems are something like reverse Amber Waystones if you aren't actually going to use them, and Amber Waystone is a powerful card in control decks that want to use their life total as a resource. If we were actually interested in decimating emblems at 5-6 power then they might be worth it, but I really think we aren't. (If there were maindeck Temples then emblems would be more appealing since the 2/2 bodies would be more important.)
11) As you would guess from my 82% winrate with the deck, most matchups seem extremely favorable to me. The main matchups that feel close are Rakano (which can assemble a lot of threats very quickly and overload your removal if you don't find a smuggler for Malediction) and other Incarnus control decks (mainly since Wasp is bad against them - that said, they usually have some bad cards against you as well).