Swap Underdark Rift for Ominous Cemetary; very similar effects but the latter doesn't require a d10 (funny, but not ideal for convention play).
Move Screaming Nemesis, Pyrokinesis, and Sentinel Dispatch to the Hall of Fame.
Add more support for dedicated storm deck Helm of Awakening, Lotus Bloom, Gamble, Vessel of Volatility, Strike it Rich
Give midrange a few more anti-aggro tools (Mogg Mobb, Wall of Earth, Invasion of Karsus) as aggro has been running the table recently.
Cut some underperforming 4-mana dragons and upgrade them to 6 mana dragons; goes well with the Dragonlord's Servant->Urza's Incubator swap.
Go up on forks and X spells as finishers for control (who doesn't love forking a 10 damage fireball?)
More support for draw/discard/madness synergy as it seems to finally be viable.
Cuts
Adds
Cards to help support discard synergies. Very curious how these play. I still don't think that discard/madness type synergy can support an archetype in itself, but it may be a subtheme or minor synergy in some existing ones. I'm curious to see if any of these cards end up being good enough, especially with some of the newer creatures that rummage incidentally (e.g. Veronica, Dissident Scribe, Reckless Detective)
Adding Hall of Fame cards to the maybeboard.
Major update - includes multiple paper-only iterations that didn't get reflected in Cube Cobra between drafts.
Adding tags to cards to keep track of which decks/synergies they really help enable. This is not intended as a draft guide; it's really for my bookkeeping as cube maintainer. This data makes it easier to find replaceable cards. E.g. there are a lot of generically strong 4 and 5 drops that don't specifically enable any one deck. It's good to have generically powerful cards, but there are far more generically powerful cards than I have room for.
First pass, covering about half the cards.