Good archetype support, if a bit boring: Barbed Spike - Good all around archetype support (aggro, flyers, pants, tokens, artifacts) and just a solid card in general Legion Vanguard - Sac outlets that don't need to combo to be good are rare Sinister Starfish - Filtering yay Arcus Acoltye - All 4 abilities sound good even if I have doubts about outlast Abundant Harvest - Filtering yay
Barbed Point is finally an upgrade to some really old cards. Also free pants support.
Tireless Provisioner is a great dedicated ramp card with repeatable lifegain + storable mana, but not accelerating 4 drops and trading down on mana vs removal makes it way worse elsewhere.
With how multicolour friendly our duals are Glinting Creeper isn't that hard to get big. A 5 mana 8/8 isn't too unrealistic, though it is a bit boring.
Arcus Acolyte having lifelink and reach on a growing body as well as a build your own anthem seems pretty solid. That being said, I'm a bit hesitant since I was not impressed by outlast in the past. Obviously great if you support +1/+1 counters.
Herd Baloth might be justifiable with only heavy combo support. It and Scurry Oak go infinite with Ivy Lane Denizen, but they both also work with the +1/+1 on etb cards that enable the persist combo. Renata, Called to the Hunt, Grumgully the Generous, Good-Fortune Unicorn, and Rhythm of the Wild are 4 entirely reasonable cards that turn Herd Baloth into 2 5/5s. It's a lot of specific cards, but even just in RG you can have 4 enablers, 2 Ivy Lane specific pieces, 2 persist creatures, then Goblin Bombardment + alternate sac outlet of choice, which is a lot of redundancy for infinite combos that is playing reasonable midrange cards.
Prophetic Titan being expensive and needing delirium makes it a bit hard to recommend over most UR cards that see play but it is an incredibly abusable card with a bit of work. Using the etb impulse to find reanimation/blink effects makes it into a single card engine in the right deck (It + Ephemerate is reasonably close to lethal by itself). Without blink/reanimation I think its powerlevel doesn't make up for how much more expensive and clunky it is than most played UR cards.
Needing to trigger delirium on Dragon's Rage Channeler to get the payoff of a 1 mana 3/3 flyer with a downside just isn't that good in most decks. The surveil is nice but is most impactful late in the game, which goes against how aggressive the payoff is. There's certainly some decks that want this card, but in general aggro doesn't like its inconsistency and dedicated spells matter builds have better (and less fragile) payoffs.
Junk Winder is great but entirely in the wrong colour. In blue it's pretty heavily restricted to Whirler Rogue/Talrand's Invocation/Kasmina, Enigmatic Mentor, which makes it incredibly dependent on other colours while being CC and having an incredibly bad worst case. If it was 6U I would probably test it with the intention of mainly splashing it, but that's not really doable with 5UU.
Scurry Oak being able to go infinite in mono-g with only 2 cards is pretty neat, especially considering both are alright by themselves. Without synergies you're looking for 2 triggers for it to be great, which is pretty reasonable. Admittedly 1/2 evolve is way more awkward than Crocanura's 1/3 evolve, so I could see it being too clunky.
Jade Revenge Frog is a pretty boring beater. Blocks, gets in for 2, and has 2 words of rules text.
Abundant Harvest is a good card. Only awkward thing is that it's purely consistency, whereas the blue cantrips easily support spells matter.