I haven't got much to contribute about the OP's idea, but...
How about instead of fully split armors, each armor takes a percent damage based on whatever the armor was hit took.
For example, say an enemy has 100 physical armor, 200 magical armor, and you do 50 physical damage. You hit the Physical armor for 50% of its maximum, so the Magic armor ALSO takes 50% of its maximum, or 100 damage.
So you have a weapon which deals fifty (50) damage, and you are attacking an enemy which has one hundred (100) Physical Armor, and two hundred (200) Magical armor, and your attack with your 50 damage weapon deals a total of one hundred and fifty (150) damage. ... Ummm... that's not how math works.
There is no skill or weapon in the game which deals 50% of the target's armor in damage. It's nonsensical.
Try explaining your idea again without using percentage-based numbers which don't apply.
Your solution would only make things more convoluted. Phys gets a bonus against phys armor and does less to magic armor? So you're telling me that my mace is more effective against that guy stacking plate than the one in robes? No, the problem with armor isn't that it failed to accomplish what it was trying to do, it's that it accomplished way more than what it should of done.
The point of armor was to prevent hard CC being king. The way they fixed it however does two things that don't make a whole lot of sense.
1. The armor system replaced the old one in it's entirety: The shield armor system makes sense when you talk about it from the standpoint of removing CC, but when you start applying it to all attacks at the expense of the old system, it feels one dimensional and boring. Having the shields be reduced exclusively by attacks with hard CC effects in combination with the old system from D1 OS would make much more sense. As of now you save your knockdowns for after you standard attack the enemy's armor off, leading to a hilarious amount of back to back stuns. Having to actually use multiple knockdown skills before you could get one would better balance the amount of effort needed to obtain the powerful effect of skipping an enemy's entire turn. It wouldn't even be hard to do, just keep D1 os's system and just make the willpower and bodybuilding skills grant the CC armors, which would only be reduced by the means stated above.
2. Non turn skipping effects are also blocked by armor: Many effects in divinity are very interesting to use and can provide interesting ways to fight a battle. They are rarely, if ever used. An ability that makes the enemy bleed fire or unable to move sounds nice, but it's decision between those skills and skills that simply skip the enemies turn in it's entirety. Because the armor system blocks these attacks evenly, the lesser effects see little use. I find it strange that the armor applies to them in this way, as I don't really recall anyone saying that shackles of pain or burn DOTs were overpowered in Divinity 1 OS. Just let these abilities go through armors, them being actually useful would add immeasurably to the variety of the game.
Overall, the idea of these armors is a good one, it was just applied with way to broad of a brush and needs to be tightened in scope. As of now it suffocates many other systems in it's current bloated form.
This idea does seem better than the one in the OP. I have increasingly started to use my hard CC skills to damage armor faster because by the time I get it off, the cooldowns are almost refreshed.
It only does 150 damage if you think of armors like a combined pool. Think of armor like a single total with a modifier for how effective it is vs magic or vs physical. So the same 100 points of magic-focused armor are twice as good against Magic as they are Phys. In that sense, your 50 phys damage strips 50 armor, but 50 magic damage would only strip 25 armor because that armor is twice as strong.
This is functionally equivalent to having 100 and 200 armor, where 50 phys strips 50 phys armor and 100 magic armor simultaneously.
I like the core idea behind armor system but I personally don't think the current implementation is good for the game. Just like you said it forces you to focus on either Physical or Magical because if you do not, you have to go through 3 different buffers instead of just 2. Making almost all encounters more tedious than it needs to be and for what exactly? I can't see any reason other than just goofing around.
My solution to this problem would be to shatter both armors if one of them breaks. This would further encourage hybrid parties and would give a new meaning to skills like Chloroform.
Other than that I do not have much problems with armor system. I think CC part should remain the same.
This suggestion at first glance might feel like it might make the game way too easier but remember this goes both ways.
This is exactly what I am suggesting, except that I think both types of damage should contribute to shattering armor. If your target has 200/200 armor, and you do 100 phys, 100 magic, and then 100 phys damage, normally that 100 magic damage would be a total waste. The armor is shattered when you hit that last Phys point, at which any magic damage you have done so far may as well not have happened.
You COULD simply have a single 200 armor total that blocks both physical and magical damage, but doings so takes away the ability for characters to be anti-phys or anti-magic focused, which is pretty cool. By splitting the pool but damaging both in proportion like I originally suggested you can keep that. The OTHER way to keep it is to have physical/magic resistance, which works exactly like the existing elemental resists, and makes hitting with the preferred type more efficient. However, I like the way the current armor system displays, as it's much easier to see that someone has 2500 physical, 500 magical armor and is therefor weak to magic, than it is to inspect them to see that they have 80% physical resist and 0% magic resist, with 500 armor. Plus that resist would apply to armor only and not vitality, adding to the confusion.
