Due to the way this set has been spoiled I don't really have any ordering method so it will actually be random as opposed to just appearing that way! I have also never reviewed cards purely from a text document. It shouldn't make a difference but it really feels like it has. I just don't have any real recollection of these cards due to the lack of visual identity for them.
Teferi, Hero of Dominaria 6.5
This is a very solid planeswalker indeed. Sadly it is five mana and two colours. Two colours that have so many top tier five drops that getting a look in is going to take some serious out performing of my expectations. I have set that bar pretty high and so I am not expecting this guy to last long in the drafting cube. I do still expect Teferi to impress when played. The Temporal Archmage version of Teferi was an impressive card and Hero of Dominaria does most of what Archmage did for you in a single ability. Either Archamge drew you gas or he untapped lands and let you pass the turn in safety. Hero of Dominaria does a little bit less of both but at the same time and gaining loyalty, from one place down the curve as well! Teferi can effectively cost only three mana. He is perfect for a control deck. The -3 is outstanding as well. If you need to deal with something you can. Teferi, Hero of Dominaria is super on theme and has a very broad range of abilities. Mana and cards are always good and broad removal usually is too. His ultimate should win the game pretty well although the general control and value he offers should do that for you anyway. Power wise I think this Teferi is the best Azorius planeswalker printed by a decent margin, I also think he is the most powerful five drop walker in white or blue presently. Sadly I just expect Tamiyo to remain more frequently played by a good amount due to being mono coloured.
Jaya Ballard 3
A good nostalgia hit but a little bit lack luster on the function. While the power here is fine the issue is how narrow this package is. In the wrong deck Jaya really doesn't get a lot done. She is very red and very focused on spells. Only two archetypes fall into those groups. She is a bit too top end for most decks wanting to go nuts on burn spells and so that feels like it only leaves red ritual based decks that will want her. I think she will be a nice addition to such things in cube but that is such a narrow application that Jaya shouldn't be much of a consideration for a main cube slot in most cubes. I like her a lot and will be doing a couple of build around decks for her but I don't expect great things to come from her that often. Jaya really needed a way of protecting herself without relying on cards in hand to shine.
Urza's Ruinous Blast 4
Well this is quite interesting! Not how I thought legendary spells would work but that is not a criticism. This card is absurdly powerful but I think I have to put it in a class of cards along with the miracles. If you build around this then it will be very strong indeed. When you have great flash legens like Venser and Avacyn, sticky dorks like Kytheon and walkers like Gideon of the Trials then the Ruinous Blast is aptly named. That would be a very powerful and swingy effect if you lost the legend, the fact that you get to keep your Avacyn makes it pretty extreme. You should be winning off the back of that in much the same way that you should be winning when you setup a well timed Entreat the Angels. This might have enough power to merit trying to support it in cube but it will be a pretty awkward draft card even with a load of support. I think the fact that this is so onerous combined with the fact that you will just randomly lose to them having the wrong legend from time to time makes it not as consistent as you want this sort of thing to be. This is Akroma's Vengeance far more so than it is Planar Cleansing and so you will need to have a deck that is also good against walkers to run this sort of tech.
Karn's Temporal Sundering 1
Good job they stuck the self exile aspect on this else it would be an easy modern Time Vault Key style combo with Eternal Witness! Anyway, despite that I don't think this is great at all. I am not sure it would be exciting if you didn't need a legend in play to even cast it. It would certainly be devastating to slow clunky decks only making big things but to any sort of aggressive deck this is just worse than a five mana Time Walk without a bounce spell tossed on.
Jaya's Immolating Inferno 1
Well designed but as such to fair and contained for cube. This isn't even as good as Arc Lightning at three mana and it never scales as well as Fireball as a finisher. This is only good as a way to swing a board in a big way, indeed reminiscent of Bonfire of the Damned! If you kill a couple of useful dorks and a planeswalker then great but if you just do some minor face damage and kill a thing then this is low value and very low efficiency. It is one of those awkward double situational cards which I feal rules it pretty well out of contention.
Kamahl's Druidic Vow 0
Such sillyness! In the perfect deck this is quite nuts but such a deck is full of legends and lands and doesn't sound very good beyond the times it gets to play this for eight. This is one of those cards that scales up with itself so the more mana you put in the better it gets and at a much fast er rate than other mana dumps. The issue is that at the point at which X is high enough to be good value and worth playing it is already a completely overkill card.
Benalish Marshal 6
This is a narrow card in that you only want to play it in a mono white aggro deck but luckily for it that is one of the very few well supported top tier archetypes. In any other colour this would presently be very weak in my cube but in white, the colour of Spectral Procession, this is all sorts of fine. I am not sure that it is better than Glorious Anthem at being an Anthem but it is a more powerful and a more rounded card. You can play Marshal in an equipment heavy deck. He does something on his own. He is a vast tempo card when you do get to goldfish with him. All round I think it is a pretty fair card that white weenie decks quite want. It is sufficiently on theme and powerful that you just have to play it when you can, again a bit like Procession. He is not as potent as Anthem simply because he is easier to remove and having your Anthem dealt with can be quite brutal but that will not stop it seeing play.
Tempest Djinn 2
If any old island could power up the Djinn it would be a pretty scary card. With only basics working for it Tempest Djinn is far too narrow. You only want this in a mono blue deck that wants to do creaturey things. This card has some minor application in devotion blue and skies style aggro blue but these are not tier one decks that we are talking about. They are not even decks supported by most cube builds.
Steel Leaf Champion 1
About as narrow as the blue one and generally less powerful too. You might play this in a mono green stompy deck, a deck which occupies one of the lowest tiers you still bother to classify! You might pack it in a green devotion deck but it would be fairly off theme in such a build. I'm not really feeling this one. Leatherback Baloth has not ever made waves nor is he likely too and these two cards are much of a muchness.
Goblin Chainwhirler 5.5
This is the hardest to know of these four. I am not a fan of the card as it is pretty polar, either it is a pretty mediocre Trained Armadon or it is a 3 mana Wrath on 3/3 legs! The times this card is good it will be utterly devastating and the rest of the time it will passable. It is slow and clunky enough that red decks may just prefer to start going face than clearing boards with this kind of card. I think this is probably just too powerful not to be good in cube. The cost of this card is quite bound up in the triple red aspect. With red commonly going mono you easily negate that cost and wind up with a rather pushed card, say like Rampaging Ferocidon, that is mostly fine and sometimes is unbeatable. Cost obvioulsy makes this a chunk worse than the dino but probably still in the realms of cube worthy.
Knight of Grace / Malice 0
Pretty spot on re-imagining of Black and White Knights. These are appropriate power level to represent such cards in a modern setting. I love the change of protection to hexproof from. Protection is not a good thing to link to a colour as it is too uninteractive. Great though these are I don't see them cutting it in the cube.
Merfolk Trickster 5.5
This is absolutely good enough to pack in a fish deck being one of the best tempo plays and creature disruption such a deck has in tribe. I think this card may also have some hope as a stand alone card. It is super versatile and is very good both with and against planeswalkers if trying to take them down in combat. Flash dorks are just right up blue's street.