Geosculptor Yip (4): Pseudo Taunt 4/8 for 8 mana, it has a decent chance of living for a turn and you might be able to work some armor gains into a big turn, but this card is a much worse Y'Shaarj, Rage Unbound overall. 

Skull of the Man'ari (5): Odds of weapon removal the turn after it's played is low, so you can find some value from it casting a demon at the beginning of your turn, however, drafting demons isn't necessarily a sure thing, and then you need them in your hand when this is played to get value from it. Overall just not a viable card by itself in Arena. 

Unstable Evolution (1): Very cool mechanic and design. Great flexible card for Shaman. Overpaying slightly for flexibility is pretty normal for card design, but this card gives flexibitily a totally new bar. Thing is you might get carried away with playing it, which might get a bit too expensive. 

Unstable Evolution Rating 1(Excellent): The fact that you can evolve one or several minions multiple times in one turn is pretty amazing and offers great value.  If you play a 5-drop on the following turn you could potentially upgrade it to a 10-drop!  It's very flexible in how it can be used and I would expect all sorts of crazy combinations and shenanigans with this card.  Be prepared!

LEGENDARY: 

Aluneth Rating 4(Poor): At first, it seems average (compare to Nourish and Sprint), but you'll quickly start milling yourself, and you won't have a deck with enough low cost cards in arena to compensate with a hyperaggressive playstyle.

Dragon Soul Rating 5(Terrible): Just bad. Unlikely to get even one activation.

Geosculptor Yip Rating 4(Poor): Not that terrible, since 4/8 isn't that bad and it could live a few turns, constantly spawning 2 mana minions, with a chance of getting better stuff. Still below average.

Grumble, Worldshaker Rating 1(Excellent): Great card. 7/7 for 6, with a battlecry that will do good probably as often as it would harm. There's a bunch of strong common battlecry minions, and returning them to your hand can also be considered heal or carddraw, if you get to return some damaged minion. And let's not forget that they cost just 1! So basically, if you're forced to return 1 minion, you can play it right after and still just paied for vanilla - nothing for heal or a potential battlecry.

Kathrena Winterwisp Rating 2(Good): Borderline to excellent. Will almost always provide more stats than vanilla, with a potential for some insane Tempo turns with a Savannah Highmane or Charged Devilsaur.

King Togwaggle Rating 5(Terrible): Just bad, nothing to discuss here

Lynessa Sunsorrow Rating 5(Terrible): Waaaay to expensive to pay off. I wouldn't even call this draft dependent, the card is just way too inconsistent.

Marin the Fox Rating 3(Average): Poor in tempo, but potentially game winning. However, only in situations where you're slightly ahead of the game, or have some Crazed Alchemist shenanigans. Thus, more a win-more card most of the time and thus average.

Rin, the First Disciple Rating 4(Poor): Battlecry is pretty much worthless, so what's left is a 3/6 taunt. For 6 mana, that's poor.

Skull of the Man'ari Rating 4(Poor):  Your rarely have enough demons to get value, but if you manage to get 2 activations off it which are not for 1 cost demons, it is decent. Still too inconsistent to be average.

Sonya Shadowdancer Rating 4(Poor): Similar to Cult Master, but worse. 2/2 for 3 often is a worse deal than 4/2 for 4, and the 1/1s will only help if they have a strong battlecry or Combo. Inconsistent, thus poor.

Temporus Rating 5(Terrible): I love the concept of the card, but it is just not good in arena by any means.

The Runespear Rating 4(Poor): If it only was cheaper... The discover spell mechanic might end up pretty good, as you're often able to pick something that clearly benefits you, and you always have the chance for a boardclear with Volcano. Kinda inconsistent still, and a bit too expensive, thus poor (borderline to average)

Twig of the World Tree Rating 2 (Good): Heropower buff / free pings for 5 turns is nice, but not great for 4 mana. Deathrattle can be ignored, unlikely to get anything of it, you will have 10 mana already most of the time this breaks (rated 3 before update). UPDATE: I assumed empty crystals and thus didn't consider you get your crystals refreshed after breaking it. If you get to play this card early without losing too much tempo, you basically won. Kind of risky to spend 4 mana on a 1 attack weapon in the earlygame though, and the risk of running out of steam later on is what holds it back from being excellent, imo.

Zola the Gorgon Rating 3(Average): A slightly better carddraw as you have control about what you draw, but that's already it. Fair stats, average card.

Quote from Aeris >>

Twig of the World Tree Rating 3 (Average): Heropower buff / free pings for 5 turns is nice, but not great for 4 mana. Deathrattle can be ignored, unlikely to get anything of it, you will have 10 mana already most of the time this breaks.

Indeed, I completely overlooked that, thanks. Gonna update the prediction, as this renders the card much better than I initally thought.

Leyline Manipulator Rating 2(Good): At the worst it's a Chillwind Yeti, but has the potential to give you some cheap cards with its Battlecry.

Leyline Manipulator (1): Chillwind Yeti, with an elemental tag that reduces the cost of a BS u RNG out of your ass? Hell yeah!

Skull of the Man'ari - Terrible.
You need a lot of demons to benefit from it, and that's pretty difficult to do in Arena.

Geosculptor Yip - Bad.
As far as 8-mana minions go, this one is a bit tricky. I agree that this card is hard to benefit from, as armor isn't something you consciously get in Arena, but I do see small potential.

Unstable Evolution - Good.
Now, I don't quite understand why this card is rated so highly. It does have high flexibility and allow you to efficiently use your mana, but unless you have some combo with it (I imagine Rattling Rascal, Bomb Squad), it looks like average buff spell for me. I appreciate the fact that it's a very flexible buff spell, depending on your game state and mana available. Looking forward to see how it plays.

Leyline Manipulator - Good.
Good stats, and it certainly makes "add random mage spell" cards more interesting.

edit: edit on Unstable Evo rating after reading more about it

@Aeris - Rin is a Deathrattle not a battlecry.  

Leyline Manipulator (2): As a comparison, it's roughly the same as a 4 mana Ethereal Peddler, although most cards generated for Mage are usually random spells (usually better then totally random cards), I'd argue the reduction ability on this card is more powerful then the Peddlers. Most of the time it will just be a 4 mana 4/5 with an elemental tag which is a still a solid card. 

Evasion (2) (4): It's an absolute shame this is an epic card since it pairs so well with Sudden Betrayal just purely by playing mind games with opponents. Due to its rarity, most players won't play around it as often so they will just attack face with the smallest minion first. I can see this card or the presence of this card making situations awkward for opponents. If Evasion was more common then players might use their largest minion to face first instead of smallest leading to lots of misplays. The card is infinitely weaker against hero powers with pings since you can trigger the secret easily without using a minion. After more thorough consideration the card needs too specific of a board state to be consistently impactful. For only 3 secrets introduced there is at least some nice variety. 

Furbolg Mossbinder (4): it's a close comparison to Darkspeaker,both have an upside and downside. Darkspeaker allows the minion to keep its abilities, allows for a tempo trade and can be played as a 3/6 for 5, not ideal but it's something. Mossbinder on the other hand offers much more value with the 6/6 body, specially in the early game. The minion can't attack however so it wont swing teh game the turn its played tho. I feel the card is about the same in terms of playability, although the Mossbinder can get decent value if you can land the transform effect on a very negative minion. Edited: 6/6 has summoning sickness. 

See my thoughts to all revealed cards HERE!

Evasion Rating 3(Average): I'm undecided on this one, and although it's like a pseudo Ice Block you can still take fatal damage, depending on what your opponent attacks you with first.  It will probably cause some problems if your opponent is testing for Sudden Betrayal, but I still don't know how good it's going to be.

Evasion - Bad.
Nice defensive tool, but I'm not sure it's something you want for Arena.

Evasion needs very specific conditions to be good. If you are far ahead on ressources and about to take over board control, you can play evasion to prevent your opponent from bursting you down. But in most cases, your opponent wants to trade with your board anyway and can just use a small minion to test for evasion / sudden betrayal. You basically pay 2 mana to force your opponent to order their actions awkwardly and may put more damage into your minions than they'd want to. And if you don't even have any minions out, chances are that one turn won't save you either. 

Maybe I am missing something, but it seems like an awful arena card. 

Evasion (4): In most situations it will be more if an Ice Barrier, than Ice Block, since u will try to play it to block off some dmg (=to "heal" yourself). Rogue does like healing. But this card is just not worth it imho, if for nothing else than cause its an epic and there r certainly a lot better epics out there.

Furbolg Mossbinder (2): Situational, very much board dependant ... but DAMN! This card will be so brutally insane when u have an early curve. And good any time after to "heal" a minion or transform a token into a 6/6. Very good card.

Quote from Sinti >>

Furbolg Mossbinder (2): Situational, very much board dependant ... but DAMN! This card will be so brutally insane when u have an early curve. And good any time after to "heal" a minion or transform a token into a 6/6. Very good card.

Quote from TSMS >>

Evasion needs very specific conditions to be good. If you are far ahead on ressources and about to take over board control, you can play evasion to prevent your opponent from bursting you down. But in most cases, your opponent wants to trade with your board anyway and can just use a small minion to test for evasion / sudden betrayal. You basically pay 2 mana to force your opponent to order their actions awkwardly and may put more damage into your minions than they'd want to. And if you don't even have any minions out, chances are that one turn won't save you either. 

Maybe I am missing something, but it seems like an awful arena card. 

Furbolg Mossbinder - Average.
Interesting, at first I thought it was some kind of Bonemare, but then realized you can't immediately attack with the summoned 6/6 Elemental. "Healing" damaged minion and buffing token is good value, but that's kind of situational. Transforming minion, however, sounds pretty interesting as you can combo it after using drawback cards like Bomb Squad or Rattling Rascal. Overall, nice support ability to have in certain situations, but maybe not front-liner like Cobalt Scalebane or Bonemare.

Quote from Sinti >>

Furbolg Mossbinder (2): Situational, very much board dependant ... but DAMN! This card will be so brutally insane when u have an early curve. And good any time after to "heal" a minion or transform a token into a 6/6. Very good card.

Deck of Wonders Rating 5(Terrible: I only like to use random effects when I'm desperately digging for a solution.  With this card you never know when you'll draw the spells, what they'll be, and who you'll target.  You could be ahead and either kill yourself or the main minion that's keeping you alive.  If I'm doing something random I at least want to be able to control WHEN it's going to happen, and in that respect, be able to have some influence on the board state before it happens.

Furbolg Mossbinder Rating 4(Poor): It seems alright, but you've still got to have a minion on the board for it to be worth anything.  One thing to keep in mind is you're losing the stats from the minion you transform, so unless it was a 0/1 or 1/1 it's not as good as you might think.

Unidentified Shield Rating 3(Average): No one cares about the Armor gain, so the important thing is what you're getting in addition to that.  When you look at it, none of them are really overwhelming and the Tower Shield +10 definitely rates lower on the chart.

Quote from TSMS >>

Quote from Sinti >>

Furbolg Mossbinder (2): Situational, very much board dependant ... but DAMN! This card will be so brutally insane when u have an early curve. And good any time after to "heal" a minion or transform a token into a 6/6. Very good card.

 Best case you transform a 1/1 into a 6/6, which nets you 6/6 in stats for 5 mana. That's pretty mediocre for a situational card. This card seems below average.

Quote from DyingAtheist >>

Quote from Sinti >>

Furbolg Mossbinder (2): Situational, very much board dependant ... but DAMN! This card will be so brutally insane when u have an early curve. And good any time after to "heal" a minion or transform a token into a 6/6. Very good card.

 Not sure I get why this is being rated so highly. Seems below average to me. Compare to Big Time Rackateer which gives you a 6/6 and a 1/1 for only one mana more, doesn't depend on your having a board, and doesn't make you lose out on the stats of the card you transform. Sure you can 'heal' your 4/5 into a 6/6 after it's hit something (let's say it's a 4/2 now) but that's a Turn 5 play that gives you... 3/5 in stats. 1/1 of which is pingable off.

Has potential but I think unless you're hitting either a) a 2/2 at max (even then it's just above average because of the partial charge) or Rattling Rascal etc. then it's a meh card. Seems much better to me in Paladin or Shaman than every other class because they'll naturally generate low stat tokens anyway. 

Quote from Zashiki >>

Quote from Sinti >>

Evasion (4): In most situations it will be more if an Ice Barrier, than Ice Block, since u will try to play it to block off some dmg (=to "heal" yourself). Rogue does like healing. But this card is just not worth it imho, if for nothing else than cause its an epic and there r certainly a lot better epics out there.

Furbolg Mossbinder (2): Situational, very much board dependant ... but DAMN! This card will be so brutally insane when u have an early curve. And good any time after to "heal" a minion or transform a token into a 6/6. Very good card.

Evasion is significantly worse than Ice Barrier, I don't see how this is anything other than a 5. Doesn't help board control, highly situational card since you need to be in a losing position and at low health for this card to matter and also contradicts Rogue's dominant playstyle of a tempo class. Rogue will never be able to play control style in arena consistently due to lack of AoE.

Furbolg Mossbinder provides 6/6 stats for 5 mana when played on a 1/1 token, but that's the best case. It's more likely that you will take a favourable trade (4 into 3 drop e.g.) and be left with a 3/2 or 4/2 to "heal" back up to a 6/6. That's not bad, but not that great either on top of being more conditional than a Corpse Raiser for instance. It's a 3 in Pala and Shaman like DyingAtheist already wrote, 4 for other classes imo.

Reckless Flurry Rating 4(Poor): You can easily get a Consecration out of this for 5-mana, but you lose the Armor AND it deals the damage to all your minions too.  It pairs really well with the other card revealed with it, Drywhisker Armorer, but neither are Common, so they're going to be more difficult to draft together.  I think I would rather stick with Brawl if I had a choice between the two of them.

Drywhisker Armorer Rating 4(Poor): I can see that Blizzard really, really wants Warriors to care about Armor in this expansion, but in Arena it's just not going to be that important.  If you're getting ran over by an aggro deck this can help you gain your footing by all the Armor gain.  Otherwise, I don't see much use for it.