Just minor tweaks.
Repel Calamity helps against Murmuring Mystic, Guild Thief was too weak, and I like the contrast between Merfolk Looter and Discerning Peddler.
Duplicate lands now have different names and art. Functional reprints are against the spirit of the cube, but it helps their duplication feel less arbitrary.

In planning a big overhaul for the cube, I can't justify it. I'd be discarding significant playtest data and balance tweaks. There aren't many new cards worth trying. Accommodating cards that currently don't fit would mean cutting too many cards I like.
I want to make cards more mechanically unique. Seeing Phyrexian Rager next to LLanowar Visionary makes you wonder why the rager needs to exist. I just can't cut them until I find replacements.
I'd like more contrast of how different colours do similar things. Merfolk Looter vs Sinister Starfish vs Discerning Peddler. Cryptic Serpent vs Kiln Fiend. Warren Elder vs Elder of Laurels. Spell Pierce vs Snakeskin Veil.
Finally, I'm still deciding what my goals really are. Sometimes I concede good gameplay for salience, sometimes the other way. Are my ideas about good gameplay too narrow? Have I forgotten things I previously understood?
Best to just stay the course.

Green still feels underpowered.
I like the tone of fight effects, but Prey Upon is not performing. The word fight also causes confusion about whether it interacts with first strike or summoning sickness.
Clear Shot is exciting as it often sets up 2-for-1s that green is lacking. Every part of it matters; +1/+0 lets you kill things you can't just attack into and +0/+1 creates blowouts.
With two punch effects I'd like one deathtouch in green. I want that to be Moss Viper but Deadly Recluse plays better.
Stingerfling Spider is an example of 'efficient distribution of rate'. The upsides of Thornado (cheap, instant, cycling) aren't that important for killing dragons, so Stingerfling Spider is a stronger card despite being overcosted in the abstract.
Dryad Greenseeker and Elder of Laurels help green keep up in longer games. They can't be stopped without removal, which I dislike, but that kind of creature makes green feel more powerful.

Curse of Predation is a little too snowbally. Some of that is good, but not on something that cheap, powerful, and hard to remove. It's too similar to Ridgescale Tusker and Bone Sabres, and the templating annoys me.
Storm the Seedcore is weaker, but I think the format is friendly to it. It helps race and green needs cards with immediate impact. It's like an aura Questing Beast! Overrun would be a good fit, but time has shown it's not a fun card.

Unfortunately, this further weakens the weakest colour. Green is hard to get right in cube, often just making mana for other colours. While I don't care much about colour balance, playing green has been frustrating. I'm hopeful that green can counter the ground aggro decks that have been tier 1 so far, but I'm also looking at doing a major overhaul if it can't bounce back in our next draft.

Secure the Wastes and Hellrider are coming out for being a bit too powerful. They're close enough that if there was a cost to updating the cube, I wouldn't bother.

Secure the Wastes really shines in this cube. The combat focus and absence of crazy haymakers makes the 1/1 tokens valuable. It's also the kind of simple card the cube wants to highlight. However, the instant speed makes it too resilient to Pyroclasm, Flames of the Firebrand, and Yahenni's Expertise. It also leads to big combat blowouts that would be cooler if Secure wasn't already among the strongest cards in the cube. If I could simply change it to a sorcery I would, but for now Release the Dogs is the closest option.

Hellrider is harder to replace. It's going because red is the strongest colour and it can be a frustrating card to lose to. It often invalidates a lot of work making blockers or harshly punishes a player who can't kill it straight away. The candidates are not great.

Flametongue Kavu is the obvious choice, but red is full of removal and I personally dislike the card. The mandatory trigger is also not salient.

Furnace Whelp, Firewing Phoenix, and Avaricious Dragon could all work. I'm wary of giving red too much flying when it also has Blaze, Lightning Strike, and Flame Lash. It leads to lopsided games where you can't stop red from killing you, or you run them over because their fliers play badly from behind.

Ogre Battledriver is cool but also plays badly from behind or when flooding. Chaos Terminator Lord and Seeker of Slaanesh are similar and like Hellrider too difficult to manage with blockers.

Living Lightning is fine. I wish it was more exciting in play, but Charging Monstrosaur and Moonveil Dragon pick up the slack. Spell recursion effects are fun and you can combo it with Wander in Death/Regrowth and a sacrifice outlet. Cult favourite Steel Wall is a funny counter to it.

Regal Bunnicorn is a perfect fit; a simple design that's powerful and plays well. It synergises with Pacifism and Banishing Light, and makes Murder more useful against token decks. Ajani's Pridemate wasn't popular and I don't like the gameplay of a deck full of life gain effects.

Day of Judgment and Languish are a bit overbearing for the cube's power level.

Black gets a simple downgrade with Yahenni's Expertise; I like how expertise encourages you to run creatures with your sweeper and is more easily survivable. I dislike "-X/-X until end of turn effects" because it's an arbitrary distinction from damage. Mire's Grasp beating Take Up the Shield makes sense, because the aura is still there after the indestructible wears off. But with Yahenni's Expertise it isn't as obvious. Fortunately that's the only indestructible in the cube.

I'm fine with Sunblast Angel as white's only sweeper. I like the instant speed on Miraculous Recovery; as a surprise blocker, a flash creature for Cancel decks, or re-contextualizing cards like Sunblast Angel and Ridgescale Tusker.

Doom Whisperer is getting downgraded for power reasons. Bone Dragon is a cool parallel to Reassembling Skeleton.

Bonesplitter is less fun than Vulshok Morningstar. The cheap equip cost makes it harder to manage, and the lack of toughness boost rewards the crappy creatures and fliers that are already good with equipment. Snare Thopter isn't powerful, but is situationally useful and provides utility to all colours.

Blue was a bit overloaded with card selection. I like the gameplay of Serum Visions more than Preordain, as it's less geared towards good topdecks and more towards managing flood/screw and planning for future turns. Guild Thief helps up blue's creature count and makes blockers relevant against blue.

Mother Bear was begrudgingly included to hedge against Day of Judgment, so its time is up. Iridescent Blademaster isn't very powerful, but simple 2-drops are rare and it should be acceptable.

I don't like cards that are too similar to each other, and Kinjalli's Sunwing and Territorial Hammerskull are basically the same card. Taranika, Akroan Veteran will be replacing Territorial Hammerskull, as a Geist of Saint Traft that interacts with Lifelink and +1/+1 counters.

It's time to cut Perilous Myr.
Perilous Myr is an appealing and simple artifact that's within the power band for this cube. It's a card multiple colours are slightly interested in, which makes it a good colourless/hybrid design.
However, too much of its rate is tied to killing small creatures and blocking. The cube has too many cards that bias this way, such as Day of Judgment, Sporecap Spider, and Shock.
I wanted to provide sacrifice fodder for Skullport Merchant and Hobblefiend, but on closer inspection there's enough of that in every colour except blue and red. If anything, the cube has too many creatures like Perilous Myr.

I've been looking for a colourless (or hybrid) card to fight defensive decks that kill your creatures. If slow decks can sideboard Steel Wall against your small creature deck, you should have something to bring in against them. It should be bad on defense and resistant to Day of Judgment.

Crystal Ball fits well, a powerful card that helps you draw more spells to fight through Murder, Cancel, and Day of Judgment. It's less useful in slower decks that don't mind drawing their 6th land. However, resolving a Scry 2 every turn can easily add 10 minutes to the round timer. While it's perfect for the metagame, it wastes too much time.
Sands of Delirium, Birthing Boughs, and Whirlermaker let you win without casting any more spells. While mana sinks are useful, like Pack Rat they draw too much attention, reducing the game to managing a single card.
Snare Thopter is a simple card that's better at attacking than blocking. I like how it holds equipment, blocks Adult Gold Dragon, gives haste to //, and flying to /. However, it's still weak to Shock and Day of Judgment. It's at the top of the colourless shortlist and may replace Bonesplitter in the future.

Arcane Encyclopedia is the best fit so far. It's essentially a worse Crystal Ball, helping you draw creatures and spend mana without exposing yourself to Cancel or Day of Judgment. While it costs more mana to activate than Crystal Ball, it also draws you more land to pay for it. It's extremely simple and could see maindeck play.
It's not obvious to sideboard Arcane Encyclopedia against slow decks. Chord O Calls seemed impressed with it as a sideboard card and we've seen similar effects from Reckoner Bankbuster and Mazemind Tome.
Small creature decks can easily still lose a long game with it in play, but it provides an opportunity for them to board in a few Murders and Serra Angels to play a slower, more interactive approach. While it won't see a lot of play, when it is played it will make those games more fun.

Paradise Druid was secretly a problem in green, tricking some players (me) into playing too many mana dorks. Between mana dorks and Deeproot Champion, green spends too much time setting up and can't help overextending into a wrath. Being a hexproof creature for Bone Sabres is uninteractive and while Kaervek, the Spiteful hasn't seen much play yet, it's a reason to cut some of green's X/1s. Ornithopter of Paradise is the final nail in its coffin.

While I have aesthetic problems with Mother Bear, it's a big boon for the cube's gameplay. It doesn't require setup time, hedges against wraths, plays well with discard & sacrifice synergies, and keeps games running smoothly. I don't like how easy it is to forget to flashback, and doesn't mechanically tie into the graveyard the way Reassembling Skeleton does. Green also has a few too many Roving Harper type creatures, which might be pigeonholing the colour into Brindle Shoat + Curse of Predation style decks.

Wander in Death over Forever Young is a much simpler aesthetic tweak. Forever Young is hard to parse; it's not obvious you can cycle it or that you get one of the returned creatures right away. Wander in Death is a much cleaner parallel to Divination that is clearly for late game grinding. One of the common pitfalls with cycling is not making it clear why you'd want to discard your spell, and Wander in Death along with Unburden (another shortlisted card) solve that by sometimes doing literally nothing when cast.

The pathways were initially tested out of concern that 30 cycling taplands would be too many, but it looks like people would be fine with more taplands.

I'm representing 1x10 pathways as 2x5 allied pathways, since all other cards are 2x each