Allied/Shard Triomes 8.5
These will be staples of many formats including cube. The others get a lot of love and there is room for more. These cards play very well and are a design triumph so it is nice to have the full set rounded out so quickly. I would perhaps have liked them more along the aesthetic of the first set but it is a minor gripe alongside an otherwise uninterrupted swathe of positives. If I really had to dig for issues I could also argue that these make sac lands even better, which, as they were already the most played cards in cube and some of the highest picked, is a mildly polarising effect on the format. A side note on this is that fetchable EtB tapped lands are far less of a burden on a mana base and curving than non-fetchable EtB tapped lands. This is simply because you get so much more choice over when you deploy your tapped land allowing you to "get it out of the way" when you don't need that extra mana. The combination of cycling and being fetchable do also provide some nice tension in how you might use them and is part of why they are a design triumph. Triomes have such a significant effect on improving mana bases that heavily multi-coloured decks have risen to the top tier in my cube but I am more inclined to blame this on the likes of Omnath and Golos! Much as helping Omnath isn't a good thing helping gold cards is a good thing as they were typically some of the narrowest and most parasitic cards in cubes. The more playable they are the less they hinder a cubes performance.
Brokers Ascendancy 7.5
This is incredibly powerful and will dominate cube games pretty effectively. Even as a three colour card that I try and avoid this is easily powerful enough and some. It is basically like a slow Glorious Anthem that then starts to make more Anthems. One that also helps planeswalkers out as well! That will make this a great midrange card as well as a solid aggressive one. There are really only two ways to beat this card, one is to instantly answer it and the other is to be so far ahead you can win the game before it has done too much in the way of damage. Try and play into this and you are just going to lose every time. It isn't quite as punchy and immediate as other team buff cards but it does not take long to quickly outclass them.
Maestros Charm 6
Great little card but not the sort of thing you can really afford to fill up your cube slots with. It is a support card and a three colour one at that. Play Supreme Will in your cube instead, it is a lot weaker but it can be played in a whole lot more decks. This has a good blend of abilities, two with decent power level, one that is always useful, one that is disruptive, and one that is a situationally useful effect you wouldn't play if not being on a modal card. While this is a great card it is great thanks to versatility, not the end result. Power wise you are rarely pulling ahead when playing this. It will feel nice to have in hand but when you come to play it there will be no big swing in your favour as there is with cards like Kolaghan's Command.
Obscura Charm 6
Nice little control tool with removal mode and Negate like modes. Better removal than Dromar's Charm but less impressive counter. Ultimately a fairly similar sort of affair and so ultimately still too narrow for the power level.
Cabaretti Charm 2
This is narrower than the Esper and Grixis offerings from the Charm cycle with no default fine modes and rather too much in the way of situational stuff. I might consider this in some tokens builds but it is one of those things you play because you are tight on space and are trying to cram a lot of different things into your few spare flex slots. In reality you are probably just going to be better off running some powerful or efficient removal spell over this like Unholy Heat or Prismatic Ending.
Raffine, Scheming Seer 6
While very good and certainly above the bar on power level for cube I do not feel it is by enough to offset the high gold intensity of the card. If you can attack the turn you play this then it is a pretty massive deal but if you have to wait a turn to attack with Raffine itself then it is a bit slow for my liking. You have to be somewhat aggressive with Raffine for it to be good and the returns on a slowly growing glorified looter do not lean into that. Raffine is a very midrange card in terms of return but you cannot easily access those returns if you need to be using your board defensively as midrange decks often are. Absolutely there will be plenty of situations where Raffine just flops down, grows something immediately while looting into a perfect hand and then carries on to grow herself multiple times in short order and close out the game pretty much singlehandedly. Just not often enough, much like the amount of play Raffine will get. There are less restrictive cards that are more useful to have and ones that are more powerful which rather hamper this ones chances.
Lord Xander, the Collector 3
Well this is quite nasty. I am not impressed with this dude being in play all that much but when it comes to entering and leaving play Xander gets it done. Stock in Flash will be going up. At least the on death effect isn't too significant on the first turn of the game thus keeping this somewhat fair. I expect this to see play in some form of cheaty decks and in EDH but not so much in the way of fair and conventional use. Usually cards of this level of naughtiness have clauses on the effects like "if you cast this from hand" or an inability to be in a graveyard courtesy of a reshuffle . Xander lacking these things invites abuses. Despite this it is still going to get less action than Archon of Cruelty and not be too much of a big deal outside of EDH.
Jetmir, Nexus of Revels 1
This is kind of bad unless you are running big token generators like Secure the Wastes. Like, if you have 9 dorks you should have won regardless of Jetmir. Mostly this is an overcost Woolly Thoctar, sometimes it is a overcost Benalish Marshall, the rest of the small remaining time it is just massive overkill.
Riveteers Charm 7
This is outstanding but even at 100% inclusion rate in Jund decks it probably isn't getting quite enough play. Further to that I can see it getting left out of the main often as well. Three drops are one of the most abundant slots and when you are three colours you will have a lot of options. The cube is full of all the best cards and so ultimately cards with more raw power are taking the slots this fine card could have. Even so, this is solid removal with a good card advantage mode and a bonus situationally useful mode to round it all out. This is never dead, it solves a lot of problems, and it has a near perfect array of abilities, one of which is arguably above curve! It is about as good as a three colour three mana charm can be but that just isn't quite enough.