Imbalanced Guard & Glancing Blows

I haven't found a cut and clean explanation of exactly what this keystone *does* - other than double your effective armor.

Glancing Blows seems pretty straightforward - if you block, whatever you got hit by still does 50% of it's damage.
Okay, seems simple.

And *THEN* it is mitigated by your defensive layers?

So, with glancing blows, if you blocked 100 phys, you'd take 50. If you had armor mitigation of 25% - would you take 25% of the hundred, or 25% of the 50 that got through?
If you block 100 points of an elemental hit is the 50% getting through *before* or *after* your ele resists come into play?


Now - Imbalanced Guard
It says 'max damage reduction for *any* damage type is 50%' - which, on its face, is about as clear as MUD.

So, are you taking 50% of what gets past your elemental resistances? Or of what *HITS* you first - of which 50% of its damage gets through regardless of your resistances?

Now, a full on armor spec Jugg can achieve close to 90% phys (and with the money actually reach 90%) which would make taking this node pointless since that cap gets maxed out at 50%? Is it more for builds that are never going to realistically achieve more than 50% natural phys mitigation?
What about poison? Bleed? Or other non-elemental hits or DoT effects?

Now... if you got both of these nodes (realistic for Marauder/Templar) and a good number of block nodes (staff/shield/dual-wield) - how do they work together? Or do they *not* work together?

If you're taking 50% of what you block, does that then parse into your doubled armor to be further reduced before the final 'max reduction' is calculated?

(doing a forum search returned no useful results, just parts of build guides. And there's not treatise on the wiki on how these nodes function individually in a game-mechanics sort of way).

https://pathofexile.gamepedia.com/Receiving_damage

The "50% damage" Glancing Blows gives means that Blocked attacks will have an efficacy of 50% rather than the usual 0%. So, a 100 Physical hit blocked with Glancing Blow will have a "base" damage of 100*0.5= 50

As you can read, blocking happens before damage mitigation, so your armor will try to cover that 50 Physical you are taking.
Bear in mind that armor's "physical damage reduction from hits" percentage offered by the tooltip is a vague approximation and should not be relied upon. The actual formula is a bit exponential, but basically having a high armour will make you pretty much immune to low-damage physical hits, but will do naught when getting high-damage ones.

If it does not make sense to you, a GGG member (Mark, I guess) gave a very efficient analogy. It was someting along, "If you have a full-armour and I throw a bunch of toothpicks against you, you will barely feel it. If I run over you with a train, your armour will have little to no efficacy in saving you"

That said, Armour do mitigate physical damage from hits, while helped by EC and any other source of "physical damage reduction". That said, a character's maximum damage reduction is 90% (this applies for every damage. Chaos Inoculation and legacy Immortal Call are/were two exceptions). Imbalanced Guard put this limit to 50%. So, your armour, EC and any other source of Physical Damage Reduction will work together on that 50 Physical of the blocked hits in order to reduce it at best, but they will not be able to reduce it of 90% as they should - they will reduce it of 50% at best, turning it into a 25 Physical Damage taken item.

This, of course, does not take into account Overwhelm mechanics and Increase Damage Taken

(side note: Read all of the list of things that happens when you receive ONE hit. Then, multiply that effort for 100 times. Then wonder why you lag so much when you are in the middle of a 1 vs 150 battle)

According to what i took away from a couple of Mark_GGG posts on reddit, the core part you need to understand about imbalanced guard is that it only affects additional reduction effects. Currently this is limited to armor, Endurance Charges/Enduring Cry Buff and additional physical reduction affixes from gear. Resistances do not count as additional elemental reduction and less/reduced damage taken effects are also a different matter. Glancing blows falls into the latter category.

So when you take a physical hit, you will take 50% less damage due to glancing blows and then your physical reduction will kick in with, lets say 3 end charges for 4% each making 12% + the reduction you would get from your doubled armor value up to 50%. Then stuff like fortify/arctic armor would also come on top. I am not sure regarding the order with glancing blows though. Normally less damage taken effects apply after reduction but i am not sure if glancing blows is handled exactly as less damage taken internally or if it's it's own thing that just works similar and therefor works before reduction.

Generally the point of imbalanced guard is exactly what you said, helping builds who would otherwise struggle to even reach 50% reduction to get there.