The game, its balance and philosophy

Following Kripp's videos, people argued for changes to the armour formula. I believe the philosophy behind defences needs to be looked at more fundamentally. In the following I will in part detail why the formula itself isn't the problem.
The problem with the perceived weakness of armour has everything to do with its identity and current lack of player agency. Armour's identity is that of mitigation. In the current state of the game, few things that CAN kill you actually deal physical damage. Players mostly die to nasty combinations of ele map mods like "damage as extra" coupled with penetration etc. While every other form of defence works against elemental damage, armour does not. I strongly believe that has to change.
My suggestion is to either bring back "damage taken as" modifiers or "armour applies to elemental damage" specifically as affixes on armour gear to allow for rewarding-feeling mitigation. I suggest you learn from PoE1's mistakes. Why did virtually every melee build in hardcore play on Jugg? Because it was the only way to truly mitigate damage as an armour based character. You cannot repeat the same mistake of only tying true mitigation to very niche parts of the game like single ascendancies. As long as you don't make such modifiers widely available through generic uniques, users of other defences have access to (jewels etc.), there is no reason to be afraid of its power.
As for the formula itself, it is acceptable for damage mitigation to be weak against larger hits but strong against many small hits. It's a fair downside and every form of defence should have weaknesses.

Evasion's identity is that of taking few hits. Note the wording exactly. Fundamentally, evasion based characters should be rewarded for avoiding hits. Evasion in its pure form should be strongly tied to mechanics such as Deadeye's "Wind Ward" wherein one essentially takes less damage from hits if they haven't been hit recently. This, in turn, means it's stronger against larger hits and weaker against many hits. Note how antithetical armour and evasion are, but that's a problem deeply rooted in PoE. Still, you have to commit to respective identities.
AoE's being unavoidable is currently evasion's greatest bane and the reason why pure evasion characters are not viable. What Acro should fix for evasion based characters, evasion + energy shield hybrids simply do better. This needs looked at.

Energy shield's identity is that of a buffer. I wouldn't mind the very large increases one can find for energy shield currently if the downsides were more apparent. You could tie massive increases to ES to increased damage taken, a real downside, unlike recharge shenanigans. They get stunned less often through ready access on the tree (threshold based on ES nodes) and as such ES is ideal for glasscannon caster types. Its weakness is DoT's.

Naturally, hybrid versions of these defences have overlapping identities and require more nuance to balance.

Now PoE2 also made mana a viable form of defence in some sense. In fact, a pure mana build (Eldritch Battery, MoM, CI) has so many downsides (you cast from your EHP pool, you have no stun threshold by default) that it should in theory be the strongest, if one can overcome those downsides.

Melee does kinda blow currently. You decided not to release Druid because, I suspect, you needed a minion cuck class on release. Every non-minion player wouldn't have heard the end of it, so god bless. Still, it means the greatest upside to melee, the new weapon swap tech, cannot be taken full advantage of. Once new melee classes and weapon types come out, we will reach the promised land for melee players. However, melee classes' defence of choice is the aforementioned damage mitigation. I can't stress enough, how badly that needs looked into.
As for Monks, try as I might, playing anything other than the glorified autoattack builds made little to no sense with quarterstaves. This ties into ailments, which I will talk about later.

The decision to allow individual support gems only once per character is a fine way to balance, but I believe it fell flat completely. The idea of having to combo is great, but you run out of usable supports way too quickly. If I'm playing a bleed build, I want every ability I use to align with this identity. Yet I run out of support gems after half of one ability. Instead of typing up a storm on this, I will simply suggest this: 10x the support gems, go crazy, remove more-multipliers for all I care, but don't make me dip into ignite when all I want to play is bleed. Fuck them noobs, you reeled them in, now confuse them, trial by fire.
On that note, remove the ridiculous downsides from some supports (and the tree for that matter) for melee stuff. I don't want 35% more damage at the cost of 10% less attack speed. This is the itemised version of "stop hitting yourself"; uncalled for.

TL;DR the atlas is ass. I understand you put a lot of effort into making it, but you really shouldn't hold onto it. Everything about it sucks. It takes too long to load. Running shitty maps to prep towers just so I can finally run the maps I want to run, feels exhausting. Proccing a +10 breach on a Mire makes me want to log off. Precursor Tablets are worse versions of Sextants of old. To throw something out there, does the "mapping" system have to be a map or an atlas? You're a single acid trip away from uncovering the holy grail of endgames. Even if it "only" has a 2D interface like PoE1's atlas, the only thing that matters is a fleshed-out concept; which the current system lacks.

The atlas tree, I'm sure, will be iterated on, so whatever. The specific trees for the endgame mechanics being tied to bosskills feels a bit rough if you're late to the party (Audience prices), but it's mostly fine. Maybe a few more options to diversify playstyles.
As for the endgame systems themselves, Breach is absolute crack-cocaine on my Polcirkeln guy. I can't stop setting up and running breach maps, in spite of everything wrong with the atlas. I think you saw how much fun people had with it and I'm one of the few people who think you're not going to completely gut it, but instead make it a chase unique. Fair enough. Visions change.
Expedition would be in a perfect place if the currencies had any use at all. You want it to be about crafting? Ok. Unique player power? Ok. Incursion mods. You get Golden Exotic Coins from Logbooks only (on top of the regular ones); alternative way to refresh the window and guarantee one item to have such a mod, otherwise random. Olroth has a chance of dropping items with such mods.
Ritual is ritual and I've always been indifferent towards Deli. I will say, any anoint I look at that's actually useful costs an isolation, and a suffering for good measure. Bit steep sometimes.

Map completion should be map-boss kills again. If you don't want people to rush map-bosses, add a little multiplier to its loot based on the % of rares or monsters killed in the map beforehand.
Checkpoints should never have to be in maps.

Tiered rares are a cool concept, but they need to have a reasonable chance of being good at high tiers. I want to be excited to ID a tier 5. Make them appropriately hard to come by and let me filter for them.
Crafting is nonexistent at best, tedious at worst.

It goes without saying that freezing and subsequently one shotting bosses ain't it. To spitball something here, I think ailments should be tied to the "purity" of the kind of damage dealt. A two tiered system in which if your hit ONLY deals cold damage, it builds up freeze, otherwise, any source of cold damage inflicts its respective magnitude of chill. Same for shock.
Ignite feels really weird to use. If I want to play an ignite build, I want to be able to actually ignite, not just sometimes and only with single big hits. This ties into the whole "10x the support gems" point. That one support gem that makes your ignites deal a lot more damage if applied to a frozen enemy is the kind of creativity I'm looking for.
Bleeds not applying to ES is a grave oversight and makes CI stronger than it has any right to be, but that'll be fixed in 0.2. I'm sure.

I don't understand why a lot of quality of life features already in PoE1 aren't in PoE2. From control clicking currency, simple things like greying out items based on the itemfilter in the ritual window and vendor recipes for 3-for-1'ing etc., all missing.

I think you should've been more open to telling people that the main reason why we don't have good uniques yet, is because you didn't put any on the temporary "advanced" and "expert" i.e. good bases.

As an avid Arc enjoyer in PoE1, I think it's unusable in PoE2. The chain speed is so slow, which is completely opposite of what electricity is supposed to feel like; zappy. Maybe add a line that says cast speed improves its chain speed, but I know how hard you're trying to avoid extra lines on things.