A more detailed description for this would be: Why don't we have our armor lines somewhat... proper to the monsters they're based on?
For example: A wolver or chromalisk armor could have full bars of elemental defense, no piercing defense, and half bars of shadow and normal defense. This means shadow and normal attacks would be neutral to wolver-wearers, elemental wouldn't hit them very well, and piercing would shred them.
The only problem I see with this is we don't have enough armors based on all of the classes, which means this would severely change the playing field. Maybe this idea would be better saved until we have retrode, mecha knight, kat, devilite (lulz), and greaver (lulz) armor?
An example of an armor that is already somewhat like this: Jelly armor, but cut its normal defense in half and appropriate the lost half of normal defense to elemental defense, leaving no defense to shadow, some defense to normal, and tons of defense to piercing (kind of like an actual jelly.)
Knowing these forums, it has probably been suggested time and time again. I have tried using the search tool and have used autopager to sift through the first 20 pages of suggestion forum threads, having found nothing on this.
This would mean that MAJOR rebalancing would be needed. Yikes. So... it would be very difficult and time consuming to OOO.
Oh well. Rip me to shreds now! Go!
No, I'm fairly sure this is the first time it has been suggested. However, I'm going to have to bring out the old "If it ain't broke, don't fix it" because there is nothing wrong with the current system except for that the appearances of some monsters don't work out.
Having split defense (aka no normal but piercing+shadow) is not used very much already, having armour's defense split across three different defense types would be rather useless and underpowered.
Sure, you could solve it by making ALL armour have underpowered defenses, but it looks to me like its a whole lot of work with very little gain. (simply for the armour that looks like monsters to make more "sense")
A better solution would be just to swap the model files around for the armour (like make the magic armour look like wolver because it resists elemental or make the wolver armour look like fallen because it's weak to piercing) but it's rather gimmicky and again, pointless.
A lot of things in a lot of games don't make sense, that's just the game's mechanics and universe. Such as "how do trees grow instantly in minecraft" and "why does it take 30 minutes to pee in sims" and "where does knight's mist gets stored?". They're simply just assumed to be the "norm" in the dimension that the game occurs in. (sounds like a xxxHolic reference)
So, it's a -1 from me.