Version 1.0.1:
- Further balancing of all gears included in Version 1.0 with a more systematic approach.
- Gear scaling in normal New Game was changed such that early game gears are noticeably weaker than late game gears to encourage gear progression.
- NO new gear was added.
Version 1.0:
- All Witcher armors from the base game (from the basic to Mastercrafted) as well as their Grandmaster versions in B&W. 
- The Viper armors in HoS.
- All Legendary versions of Witchers armors obtainable in New Game +.
- Secondary stats on the Netflix Witcher set is buffed to the same level as the other Witcher sets in NG+.
- The Warrior's Leather Jacket craftable in White Orchard.
- The Hen Gaidth armor set.
- The Tesham Mutna armor set.
- The Toussaint Knight armor set lootable during Beyond Hill and Dale....
- The craftable Toussaint Knight set, Toussaint Knight's Tourney set, Toussaint Ducal Guardman set, Toussaint Color Guardman set, Toussaint Ducal Guard Officer set, and Toussaint Ducal Guard Captain set from BaW.
- The craftable Ofieri set and Order of the Flaming Rose set from HoS.
- The lootable Ornate set during Scenes From a Marriage.
- The lootable New Moon set from HoS.
- The DLC Undvik, Nilfgaardian, and Temerian set.
- The Dol Blathanna set and the White Tiger of the West set.
- The Nilfgaardian Guardman set lootable in Velen.
- The Assassin's set purchasable and lootable starting in Velen.
- The Geralt of Rivia and Ravix of Fourhorn gears were upgraded to Relic quality with very useable resistances. They aren't the best armors in the game by any mean, but feel free to use them to compete without being handicapped even in Deathmarch.
- I buffed the starting gear a tiny bit, mostly to help with the first couple levels in Deathmarch. The game gets increasingly easier anyway once you acquire more more levels and better gears. This should not have a major impact on your experience, but these changes are tentative for now.
- All NG+ versions of the aforementioned armors will be significantly stronger, so it is still rewarding to acquire new armors in NG+.
- While I'm at it, I also changed the reward of Master Armorer. You will now receive the exact armor you wear during that quest alongside the existing reward.
- I also changed the armor type of a few armor sets to better match with their appearances. For example, all Griffin School armors are changed to Heavy Armor, the Niflgaardian set is changed to Light Armor, the Manticore set is changed to Light Armor, etc. 

Version 1.0:

• I applied the stamina regen buff/penalty for light and heavy armor consistently as intended. As far as I know, some heavy armors actually give you a buff on stamina regen, presumably because CDPR forgets a '-' here and there.
• I fixed the stats of gear pieces that can carry over to New Game +, so that they will keep the identical stats in New Game +. I thought this is a given, yet I found that some pieces will have improved or reduced stats when going into NG+ for whatever reason. For example, the Grandmaster Feline Set actually has more elemental resistance in NG+ than in NG. In fact, it has even more elemental resistance than the Grandmaster Legendary Feline Set you can get in NG+.
  

As far as I know, the game features 3 types of physical damage:

• Slashing damage covers human and non-human opponents using sharp weapons, the Wild Hunt included. Most armors should protect the best against slashing damage, and traditionally this is what armors are best for.
• Piercing damage covers arrows and polearms. Protecting against piercing damage is more difficult than against slashing damage as any amount of force condensing at one point will be much more devastating than the same amount of force spreading out onto an area. 
• Bludgeoning damage covers blunt weapons (e.g., clubs, hammers, etc.) but also some big monsters like golems, elementals, giants, etc. Bludgeoning damage is the most difficult to resist, as the force can transfer straight through the armor if it doesn't have any absorbing or dampening function.
  

Most armors will offer some form of resistance against these 3 types of damage, depending on the design of the armor, the materials used on the armor, and how much of the body they cover. For example, plate armors are very strong against slashing and piercing damage, but whether they can protect against bludgeoning damage depends whether there are enough padding beneath the armor. Alternatively, chainmail armors are still great against slashing damage, but significantly worse against piercing damage and even worse against bludgeoning damage.

In order to conform to logic and common sense while also maintaining simplicity, my changes to physical damage resistances follow these overarching principles:

• Heavy armors provide the best protection against most types of physical damage, followed by medium armors, whereas light armors offer the least amount of protection. 
• Slashing resistance is generally high across the board, and is somewhat dependent on the material used and how much of the body is covered.
• Piercing resistance tends to be lower than slashing resistance and is also dependent on the armor material. That said, coverage is very important here. Decently thick leather/chainmail armors that covers a lot of the body can still has decent piercing resistance, whereas plate armors that leave many gaps will not have as high piercing resistance.
• Only plate armors can provide high bludgeoning resistance, assuming that there are always padding underneath the armors. Most other types of armors offer limited to none bludgeoning resistance. Thicker chainmail/leather armors with lots of padding can still provide decent bludgeoning resistance, but nowhere near what plate armors can do.
• Resistances should be spread out among the pieces of a set rather than condensing on a single piece. Chest armors still have the most resistances, followed by pants, and then boots and gloves. This is to ensure differentiation between heavy, medium, and light armor for all pieces: heavy chest pieces will have more resistances than medium and light chest pieces, heavy boots will have more resistances than medium and light boots, and so on.
  

Then, the game features 2 types of damage specific for monsters:

• Monster damage covers damage from the majority of monsters in the game, and also wild dogs and wolves. In my opinion, this is the type that makes the least sense in the game. Most monsters should still deal physical damage anyway in some combinations of slashing/piercing/bludgeoning damage. Furthermore, some monsters actually deal bludgeoning damage rather than monster damage to begin with. There is no good reason a good armor set can protect you against the three types of physical damage, yet cannot protect against monster damage. Thus, monster resistance is adjusted so that it is not too far from the 3 physical damage resistances offered by any piece of gear. To retain the unique character of Witcher armor, I still give them slightly higher monster resistance, whereas conventional gears at the same tier will offer slightly more protection against other types of physical damage (slashing, piercing, and bludgeoning) than Witcher gear. You can imagine that Witcher armors contains some unique materials (i.e., silver) that are very useful against monsters but overall not as durable as the common steel used on conventional armors. 
• Elemental damage covers damage from wraiths and barghests. These enemies shouldn't deal physical damage to begin with, so any protection against physical damage should have little to no value against them. Instead, you will most likely need some form of magic or enchantment on your armors, or you need magical materials that have inherent protective properties against these types of foes. Therefore, elemental resistance becomes the feature that differentiates Witcher armors from conventional armors: Witcher armors will have significantly more elemental resistance than conventional armors, simply because that is what witchers have to deal with compared to normal folks.
  

As resulted from my changes, Witcher armors still offer the best protection against most types of monsters. But against human and non-human foes, you may want to pick something else. There will be better options against slashing damage, piercing damage, or bludgeoning damage.

Naturally, the armor sets that offer highest resistances will be heavy armors. That said, the best medium armors will be equal or even better than the worst heavy armors. Similarly, the best light armors can potentially beat the worst medium armors. Just as in vanilla, you will generally have to choose between sword damage (light armors), sign effectiveness (medium armors), and protection (heavy armors). The differences are much larger than in vanilla though, especially in the early and mid game, so your choice will change your experience quite significantly during that portion of the game.

Of course, by end game, the Levity enchantment will remove almost all meaningful difference between heavy/medium/light armors. By the time you can access Levity, there will be very little reason to use any light armor, or even medium armors, as the differences in damage is pretty negligible whereas the differences in resistances are significant. Still, I don't think this is a major problem. Access to Levity comes very late in a normal playthrough (30,000 crowns away), and you can simply choose not to use it if you think it destroys the game's balance. 

Update 1.0.1:
As an extension of my premises, I introduce a new system where armors are balanced based on their physical resistances (slashing, piercing, and bludgeoning) only. Depending on the armor type, the material used, and the coverage of the armors, better armors will have better physical resistances.

Since I argued that monster resistance should not be independent from physical resistances, in this new update monster resistance is calculated from the three physical resistances instead of independently determined by me. Slashing resistance is the most influential in the calculation, followed by piercing resistance and then bludgeoning resistance. This is because the majority of monsters we face deal some form of slashing attack, while fewer monsters can straight up pierce our armors with fangs or claws. Bludgeoning resistance was the least important as many of the monsters that deal this type of damage are already accounted for by bludgeoning resistance already. After the calculation, I apply either a proportional buff (for Witcher armors) or nerf (for Relic armors) to arrive at the final number.

Elemental resistance remains the same.