I don't think so.
The analogy to D&D weapons falls apart on several levels.
First, D&D weapons are NOT all balanced. Some are obviously better than others for most purposes. As one handed weapons, the bastard sword and dwarven waraxe are clearly the best although they require a feat to use (well, they do for everyone except dwarves who can use waraxes as long as they have martial weapon proficiency). Among martial one-handed weapons, the longsword, battle axe, and warhammer are clearly class 1 weapons with the scimitar filling in the "I want to crit a lot" category and the rapier filling in the "for finesse fighters" category. Rapiers are generally superior to shortswords or throwing axes. Longswords, etc are clearly superior to heavy maces, morning stars, and clubs. Similarly, among the two handed weapons, the greatsword is clearly the damage king with the falchion and greataxe filling niche roles and the spear for those who aren't proficient in martial weapons.
I and many others would complain (and rightly so) if the game made a club as effective as a longsword or had the quarterstaff or greatclub doing as much damage as the greatsword.
What would people think of a modern combat focussed game that made no distinction between the damage of a deer rifle and an elephant rifle but insisted that they had to be "balanced"? Or one that equated civil war sniper rifles with modern sniper rifles. (Considering the relatively short time period included, this is similar to asking chain mail to be the equal of a breastplate).
As far as armor goes, you and others are missing the point about the mechanical balance. The difference between chain mail and a breastplate, for instance is max dex and armor check penalty. For a lot of characters--especially NPC fighters who tend not to have a high dex, the "optimal" breastplate is NOT significantly better than the "suboptimal" chainmail. Similarly, for most NPCs (who rarely have dexterities above 18), the "optimal" mithral chain shirt is not significantly better than an ordinary chain shirt. And when one does account for other differences, they are generally not more than one or two points of AC. A PC who chose to wear studded leather instead of a chain shirt would not suffer much. Even the PC who chose to wear banded mail instead of fullplate would not be too disadvantaged. The disadvantage would be real but probably not much more than that encountered by the fighter who uses a morning star instead of a longsword or a longspear instead of a glaive. (And I've seen both).
As far as the question of being optimal goes, I think it's clear that this is only true in specific environments. On shipboard adventures, I've seen a lot of clerics and paladins pulling on chain shirts or leather armor. It would behoove some low strength rogues and rangers without ranks in swim to trade their traditional chain shirts in for leather too. The same is true to some extent in the desert and other areas where the environment effects armors.
Now, as to PCs using the armors, it's important to remember that there are a lot of corner cases. The low-strength spellcasting cleric isn't an uncommon character type and frequently can't afford the weight of fullplate. (Mine wears leather armor at 5th level and has no intention of changing--no matter what she does, she won't even have a decent AC so there's no point in bothering). Fighters with a 14 or 15 dex really gain no advantage from the breastplate over their initial chain mail so until they get whatever armor they're finally shooting for they may not change. (My character still often wears her chain mail at 3rd level). Etc, etc. When corner cases are taken into account, there's plenty of difference in PC equipment at low-mid levels. (And the ones that dissappear at high levels are made up for by those who decide that they want the DMG's mithral splint mail of speed, Rhino Hide armor (although that's mostly 3.0), Celestial Armor (the real armor for the dex freak and it allows the wearer to fly), or their hyper dex makes "no armor" the ideal choice for them).
For NPCs, it's important to remember that A. their typically lower stats mean that many optimizations important for PCs are irrelevant to them and many optimizations irrelevant to PCs are relevant to them (encumbrance is typically more important for NPCs than PCs because of their generally lower strength and their lower access to things like bags of holding and handy haversacks) and B. Their financial situation is very different from the "adventurer's assumed standard. A sergeant in the army might well be 3rd level but still be wearing his army issued chain mail. It protects him well enough against most 1st and 2nd level warriors and he spends his paycheck on either ale and whores or on buying a new plow and a new field for his family to farm. Similarly, an NPC rogue may be dirt poor because of his gambling habit, etc. And C. Their typical challenges may make optimization far less relevant to them. The high priest of Heironeous in Greyhawk's temple doesn't often need to lead a war or go adventuring so the splint mail that lasted him until 3rd level (when he was transferred away from the Furyondian front and to Greyhawk city) may be the best armor he's ever found it advantageous to buy. For his position, a royal outfit, ring of mind shielding, and circlet of persuasion are far more useful than a suit of +3 fullplate.
two said:
Snippiness aside, this is the real point.
The D&D weapons are beautifully balanced mechanically, with threat range, damage, critical multiplier, reach, etc. all considered. Nobody really has a problem with how these are implemented, even if they are completely daffy from a historical perspective. Why? It makes for great game play, it's easy, it's slick, it's fun. Done. Whatever losses are made to "reality" are more than compensated for by the fun factor.
With armor, it's definately not the case. Mechanically they are horribly balanced, with only a few "clear winners" in each catgory. As soon as PC's or NPC's get to be 3rd level or higher, these armors will be used exclusively, barried odd circumstances. The only thing keeping PC's back is $$, and D&D is a money-heavy game. It's not a drawback for very long.
Imagine if everyone still used a longsword because it was the "best" weapon mechanically? How boring. Glad they fixed this once and for all.
Chain shirt. Mithril. How boring. Too bad they have not fixed this. At all.
