There are several issues overall, going to tackle them in a few sections. First, we'll look at the arts that there's a consensus are just space wasters. Then at ones that may be issue's because they throw off the power curve on the other side (AKA overpowered). Lastly I'll talk a little about what I consider key toolbox items that raise balance/game vision issues. Mostly for purposes of discussion and feedback to the devs, I think that the Under/Overpowered artifact list is fairly solid and any change would help overall balance goals. The Toolbox items are somewhat more subtle, as they raise balance issues as well, but only applicable to higher difficulties. I don't necessarily expect or even desire changes relating to these, just want to bring the issue's about them into the open for consideration.
Section 1: Under-powered Artifacts
Here is a list of the worst offenders. These are the items for which the consensus boiled down to “Worthless, needs overhaul”. Note: we didn’t get into certain types of items, namely sling ammo, Whips, and Tridents. None of us had much experience with them for comparison, and I also suspect that Whips/Tridents need a major overhaul and to generally be integrated into the game more solidly. The goal here is to help reduce excess dependence on RNG by at least minimizing the items that just take up slots and prevent the acquisition of items that are actually usable in any way.
Because I’m bad at forums and couldn’t find a convenient/easy way to post tables, I’m just posting a list of the questionable artifacts here, but for a look at our reasoning and suggestions here is a link to the spreadsheet where we go into that: https://docs.google.com/spreadsheet/ccc ... wVXc#gid=0 (Of note, Superminie and Shibari tend to offer helpful comments, but by default I have it sorted by my opinion as I just kept consistent alphabet-wise and we more or less concur on the worst ones)
Underpowered Artifacts:
Scorched Boots
Gloves of the Firm Hand
Bill's Tree Trunk
Cuirass of the Thronesmen
Kor's Fall
Warmaster Gnarg's Murderblade
Staff of Destruction
Razorblade, the Cursed Waraxe
Elemental Fury
Storm Fury
Colaryem
Flamewrought
Drake's Bane
Penitence
Dagger of the Past
Moon
Star
Sword of Potential Futures
Thalore-Wood Cuirass
Bolbum's Big Knocker
Dragonskull Helm
Rune of Reflection
Ring of Growth
Crown of Eternal Night
Bindings of Eternal Night
Prox's Lucky Halfling Foot
The Untouchable EDIT: Forgot about people with Aegis tree. This might be decent enough with it's secret proc to be usable by those classes. Still think it shouldn't be quite so secret, though
There’s another ~15 to 20 that are pretty borderline, but there’s mixed opinion on some of them. You can see those as well. The comments and suggestions are fairly scattered in quality/quantity (This job was much larger than I thought initially!), but the gist for most is there and it’ll be casually added to.
Section 2: Over-powered Artifacts
The flip side of the coin is that there are a few artifacts that are so good that they throw off the power curve and play becomes focused around them. There are really only two, from a raw power standpoint in my opinion, but others from a critical toolbox perspective (Depends on how DG feels about this, personally I love them).
Clearly Overpowered Artifacts:
Eden’s Guile: Easily get to 120% global on anyone who maxes cunning and naturally wears any cunning containing gear. Can go over 150% if you go crazy with it. Basically, allowing any character to act about 2.5 times as fast, which makes this almost necessary. At the very least, there is no character where you wouldn’t be... almost 2.5 times better off if you had it. I’d reccomend capping it’s speed bonus, perhaps to shalore racial levels.
Spellhunt Remnants: They just utterly destroy casters and mobs with lots of buffs, which conveniently covers most later bosses (particularly the last ones). It gives anyone who has them the buff-stripping power of a corrupter, in addition to it’s locking them down. Once again, like Eden’s Guile, this item is so good that any character is simply multiples better off with this item. My reccomendation is have it’s on use only exist for Zigur followers. The fact that it’s AM is completely irrelevant compared to their power, so anyone will still use them. But if you actually had to be a Zigur follower, that would both be a compelling argument for doing so and limit general overpowerdness for all classes. Or, just nerf them

Other arts that skew the power curve are subtler issues that would require more development decisions. They’re things that aren’t clearly imbalanced like the above two, but make balancing other arts difficult because they often dominate them.
Examples of Near dominant style Artifacts:
Black Robe
Telos’s Top half (In conjunction with any good dagger, beats pretty much any staff handily)
Spellblaze Shards (Rediculously amazing dps for it’s tier)
Dakhtun's Gauntlets (Just hands down what everyone should wear barring superior merchant gloves, or Spellhunt)
Just wanted to point these out, not saying that they’re necessarily an issue, or should be changed, but just noting that they are clear stand-outs of their types, so that any other item in them tend to pale in comparison.
Section 3: Toolbox/Utility Items
These are items that aren’t strictly powerful, but provide tools to classes that don’t have them that either simply make the game more pleasant (MORE OF THESE, PLEASE!), or shore up a classes weakness. This doesn’t strike me as generally an issue, excepting that there might be some classes (Looking at you, Brawler/Archer) who might completely depend on these on higher difficulties to counter their limitations. Others seem to disagree, so thought I’d raise the issue, anyway.
Examples of Toolbox Items:
Temporal Augmentation Robe - Designed In-Style: This might actually be borderline overpowered. What it does is provide one of the top 3 1-shot protections, most classes either having vastly weaker versions or none at all. It’s equivalent to an item granting Boneshield or Unstoppable.
Fortune’s Eye (and to a lesser extent, Gloves of the Nighthunter/Armor of Delving/ULTRA RARE watchleaders lanterns): Track is somewhat critical, getting more so as you fear getting 1-shot from around all corners. Plenty of ways to get this, and I think it’s a good thing and pleasant. But a majority of classes are dependant on items for this feature. I’d recommend buffing some of the psuedo-tracks (not a lot, but > 10 range, please) to reduce rng.
Burning Star/Eye of the Forrest: Basically, see Fortune’s Eye. Makes games not only infinitely more pleasant, but starts to be somewhat critical. There are other methods, namely Vision Runes (which should be buffed), and Arcane Eye. But Vision is currently fairly weak, and AE is only available to certain casters or, again, through items. I’d reccomend adding some more types like this, or adding a non-art ego that helps besides AE (not quite the same, after all). Basically they just make the game more pleasant.
Wanderer’s Rest/AetherWalk/Zemeky's Broken Hourglass: Controlled teleports/phase doors that don’t require a rune. Most classes can have plenty of these in some means or another, but if you don’t naturally have any, these are incredibly clutch to the point that they could be the deciding factor between life and death quite often.
Eggsack/Crystal Shards/Guardian Totem/All other summon items: There’s enough of these that I actually don’t think it’s an issue, as primarily for the non-pet classes they are used to soak up a turn or two of aggro/avoid surrounds. Tentacles also serve this purpose. I consider these critical to higher difficulties, and have no problem with this being part of the play-style, but some seem to.
Wrap of Stone/Hats of Earthrues/Shield of earth (particularly talent level 4.0+): Basically, utility in the form of some guaranteed escapes/breathing space. I can’t count the number of times I’ve been in situations where ONLY an item along these lines could save me, and if your class doesn’t naturally have such... Personally, I again feel this is a fairly moot issue by virtue of commonality, in that it’s not just 1 or 2 artifacts that can fill this tool-slot, but a non-art ego.
Assosiated Concerns and final thoughts
In relation to the whole "how item/rng dependant" the game is/should be discussion, one related concern stands out. Namely, the Swift Hands prodigy. While probably underused on Normal/Nightmare, it is in fact hands down the best prodigy if you're seriously min/maxing your character for encounters. It also makes balancing other things harder, such as Temporal Form, which is already handy and good, but can just become ridiculous when in conjunction with careful use of Swift Hands.
As for recommendations, it should honestly be nerfed in some way, however: while it is currently amazing, it would be very easy to make it completely worthless with many of the ways it could be changed. Prodigies already have balance concerns (which I'll be making another post on), so we really don't need another worthless one taking up space! The way I'd prefer to see it dealt with is either some limit on it's use per turn (One would be the natural assumption, but that strikes me as probably too weak). Could alternatively make it just take some small fraction of a turn, so you'd still have to worry about enemies acting/stuff ticking, but again it'd be a tough choice to determine the balancing point where it would become too weak.
Since certain devs have insisted that they actually appreciate feedback, I'm probably going to try to collaborate with some of the other players I tend to interact with on similar discussions of the other discrete balance area's, namely: Prodigies, Runes/Infusions, Races, AM vs Non-AM, and Classes.