First off, "randomness" is a pretty bad word, if you ask me. It implies that the system is "random" and not thought-out, when that is clearly not the case. There are different reasons for choosing a system like that, and they're not random.
Also one problem with these discussions is that always someone comes along and says "In the middle ages, it worked like this!!! [...]" and then gives us an example of his idea what a combat system should look like, more often than not being ridiculously complex and well, yeah, I guess pretty realistic. The thing is that we're not talking about making more complex combat systems, we're talking about a different type of combat system at around the same complexity level as the vanilla system. That's a huge difference. If you want to talk about creating complex systems, you're in the wrong thread.
If we had to choose between combat systems of equal complexity, I would probably choose the D&D system. In Morrowind, skill only affects chance to hit, and armour only affects damage received. In Oblivion, skill and armour only affect damage. In D&D, skill and armour both affect chance to hit. That's the most realistic of the three.
I am not saying I don't have them, but an RPG where reflexes and coordination to me is less interesting than one that relies more on character skill.
Role Playing Games are at least for me all about becoming another person, a person that I watch grow and learn throughout the course of the game. If the game is doing it's job right, I forget I am playing a game at all, or at least nearly. As a person in the real world, I am actually quite good at reflex based video games as I am sure many of us are. The problem is, where I might be physically good at using a controller for simulated sword play, my character when he is first starting out should svck with his sword. He should be clumsy, he should miss a lot, he shouldn't have the skill and reflexes to block an attack precisely as it comes. In oblivion, I simply do not get that feeling at all. I don't feel like I am another person any more than I feel like I am Master Chief when I play Halo.
Maybe most people like playing a badass sword-master from the get-go, but I would prefer to play a clumsy, powerless main character that grows out of his ineptness through necessity throughout his adventure. This is the kind of thing Morrowind's combat was best for.
I guess it's just a semantic difference, but a "miss" is pretty difficult to do against an opponent who is standing still. Even the clumsiest swordsman is capable of swinging at a large target. That target could easily move away, block the attack, or take the attack so that it didn't hurt at all, but an outright miss would be unlikely. Zero damage, whether you call it a miss or not, still 'feels' like a miss. Without a visual response showing you that the target has countered your attack somehow, it seems arbitrary. As a player though, if you don't mind that, go for it.
You assume that plate mails don't have padding underneath; I don't know why you would assume that. Seems to me that you would expect that there is padding and chain under there, you just can't see it what with the plates on top. Of course, plenty of mod-added armors do allow you to see that there's no padding, but that's not really what's under discussion.
True, I kind of did forget about that possibility. In that case, heavy armour would be superior in all ways (except mobility) to light armour. Light armour would still be substantially more vulnerable to edged weapons than blunt ones however. Except the armour progression ending with glass doesn't fit the same mould as leather/padded armour, but oh well.
Somebody else commented about how locational damage is difficult, given how fast the actors can move in combat. It's true, but in my vision of the ideal combat system locational damage is implemented along with "locational aiming". If you point at the head, your character tries to attack the head rather than swinging at a point in space where the head used to be. Momentum would only start to matter once the swing proper did, and it would be then that enemy movement could screw things up. The problem I guess is that the character's skill in predicting where the target will be directly contradicts with the player being in full control, so in my ideal system the player would only really control tactical decisions (where to aim, what type of attack to do, and the 'goal' of the attack - e.g. knocking the target off balance, disarming them, going in for the kill). The character might fail in the execution of more ambitious goals, and so the player would have to play within those limits. A tactically minded player would be better off than a hack 'n' slash one. My reasoning for this is that a mouse is totally inadequate for describing an attack anyway (not enough degrees of freedom), and so you might as well do that part for them.
A man can dream. If I ever get off my backside and code one of my dreams, they might even happen.