0 - unplayable in 40 card singleton
1 - effectively unplayable
2 - has low tier constructed decks it might go in
3 - has mid tier constructed decks it does go in
4 - pretty powerful stuff with several potential homes, able to perform well in lower powered cubes
5 - powerful stuff that is either just too narrow or has too many superior alternatives
6 - fringe cube worthy
7 - cube worthy
8 - cube staple
9 - unpowered cube bomb
10 - powered cube bomb
Orochi Merge-Keeper 2
Just a little bit too much work to get this tapping for two to be worth it. Perhaps in a tribal deck.
Isshin, Two Heavens as One 3
Very cool build around commander sort of thing. Too narrow both on effect and from colour intensity to do much else.
Blade of the Oni 5
Cool card but probably a little fragile and expensive to fully use. Getting something removed in response to reconfigure is a brutal setback. Getting this taken out with a ping isn't going to be pleasant either. If I am on the beatdown plan I am much more into the likes of Skyclave Shade. Worth a test but not at all optimistic on this one despite reasonable power, playability, and utility.
Reito Sentinel 1
I want a card that puts things in the bin back into the library but this lacks the broad appeal, playability and power level I am looking for in such a card.
Reinforced Ronin 7
This is not as good as it looks but it is still decent. It certainly isn't a card one should be comparing to Goblin Guide. If you want to continue beating down with this it has an upkeep of 1 mana which is pretty huge in the early game where this is likely to do much work. This should not be viewed as a one drop threat and more along the lines of filler or card quality for an aggressive deck. This will help you spend your mana and efficiently get in a few points of extra damage before cashing it in for another card. It will have some cute synergies with the likes of Purphoros too. It does have the advantage of being more viable in less aggressive decks than many other cheaper red dorks which in turn plays into the strengths of red. I expect this will get a bunch of play and justify that play with reasonable performance.
Acquisitions Octopus 2
Cool card but lacking in power and punch. Too easily answered, low tempo, and realtively low odds on drawing bonus cards.
Blossom Prancer 2
Just a little too far up the curve for what cube is after but a surprisingly well rounded and versatile card. I would rather have this than a Thragtusk in most cube decks and settings which mostly just goes to show how far we have come.
Kura, the Boundless Sky 2
Comically I might well prefer a Blossom Prancer to this too! This needs to die to get value making it not only slow but also unreliable. I am not all that excited about finding three lands and while a big token is fine it is not all that threatening. It is less than half as powerful as the death trigger on Hallowed Spiritkeeper which is pretty embarrassing for a 5 drop legend. Despite seemingly being quite powerful Kura is frankly woeful.
Roaring Earth 1
Just about a consideration for some counters decks but likely not as it isn't really removal or a threat nor is it going above and beyond on power level.
Mech Hanger 2
Sure, our non-existent low tier vehicle themed synergy deck has a cute land to play.
Kotose, the Silent Spider 1
Much of the value of this is lost in singleton rendering it a low power version of either Gonti or The Scarab God. Doubt Kotose is even getting into tribal ninja lists outside of EDH.
Mindlink Mech 2
There is likely some cool synergies or combos with this but they are not going to be found in drafting cubes. Cute enough with attack trigger dorks somewhat acting as a kind of haste giver but blue is hardly flush with that kind of card nor in need of a midsized flying body.
Touch the Spirit Realm 6
Oblivion Ring with reduced target range and a flicker mode to make up for that. Much as two mana flicker is not a card you would play by itself when you stick it on the back of a playable removal spell it gains a lot of value. Killing off tokens, saving your stuff, or just gaining extra EtB triggers are all fine things to be doing. This is a fair card with relatively low power but it stands a chance in cube for the high playability and option density. Mostly I think removal has come a long way since Oblivion Ring was a staple cube removal tool and so that is the issue this faces most.
Thundering Raiju 2
This is quite punchy but it is also simply outclassed in raw power. This hits for 4, then 5, then 6 by itself, or a little bit more should you have other dorks to buff up. All going well this is an efficient beater but little else. Going poorly however and this is relatively soft to removal and also somewhat underwhelming in combat. This being just a beater and not quite there on power makes it basically unplayable.
Roadside Reliquary 4
A bit narrow but nice to see more takes on the Horizon Canopy effect lands. This will make OK filler in decks that reliably have either an artifact or an enchantment in play and it will be outstanding in those that can do both. Especially low curve and fast paced decks.
A 3 mana 2/2 flying Fleshbag Marauder is an upgrade. Getting the option on drawing a card instead further increases the playability and utility of the card. This is no bomb but it is probably enough to do reasonable work in cube.