They're not mutually exclusive...?
So your argument is essentially that a game should become super-easy while demanding min-maxing, and that's the mark of a good game? Dunno about you, but when games get too easy, I get bored. Playing Dead-is-Dead through Dead Money is a thrilling experience, doing the same in Broken Steel is just tedious and boring because my armor's so great that nothing will possibly kill me. Likewise, when a game demands the same gear gets used over and over, that reduces motivation to replay the game. Part of what keeps me coming back to New Vegas is I can design a character with the best stats in mind to use the Medicine Stick and then compare it to a character with the best stats for This Machine and compare how the two function in best-case scenarios. Playing FO3 for the thousandth time with that god damned Android's plasma rifle just isn't as fun.
Listen, there's realism, then there's game design. You can't sit here and argue "power armor should never provide full immunity" while arguing "orcish should get you killed cause it's made of objectively inferior materials." The first statement prioritizes gameplay over lore, the latter statement prioritizes lore over gameplay. The problem is the latter statement results in about 10 different weapon and armor types becoming absolutely worthless fairly quickly, with 90% of the game being played using the exact same gear: the gear that's DESIGNED to be used at the end. The game would gain far more replay value and diversity if each armor had something to offer, realism be damned. If I'm given a choice between "but how on earth does wearing elven armor increase damage to bows" and "elven is inferior, don't use it," then I'll take the first if breaking realism seems to be the only way to provide balance. (I'd imagine devs would want to attempt more realistic traits such as movement speed first, using the unrealistic when it's clear that's the only option)
And here you highlight the point you're completely missing that's flying high over your head: nobody is saying stats should become meaningless, people are saying different armors should offer different stats, not superior and inferior ones.
Your New Vegas example is flawed and untrue; stats for armor did not become meaningless, but rather Light armor quickly became god-tier because it offered the most unique stats while still offering a decent amount of defense. Light armor did it's job and offered different stats, the failure was that medium and heavy armor rarely did. Light armor offered movement speed, crit rate and crit resistance, while medium and heavy answered with nothing at all aside from more DT. Medium and heavy need alternative stats of their own to compete, with heavy potentially retaining it's purpose as best defense simply by offering modest DR alongside DT.
You want to talk meaningless? Every set of armor in Skyrim that's not the best, defense wise. THOSE are meaningless. Interestingly, with enough time and dedication, any armor in Skyrim can hit the defense cap. What becomes the thing that makes them different when they all hit the defense cap? Aesthetics. You wanna talk dress-up dolls? Look to Skyrim. That's what happens when you do not offer alternative stats for each unique set, and that's what happens when you're so shortsighted and blind as to think objectively superior stats should ever be a thing in an RPG.
And no, there is no progression. There's an illusion of progression. In Skyrim, I get a perk to give myself 20% more damage. Meanwhile, the enemies level up to gain 20% more defense? WHAT THE [censored] IS THE POINT? There's a reason refusing to level yourself in Skyrim is considered a legitimate strategy. Compare to New Vegas: at level one, I can tank a single hit from a Deathclaw at best, or die in a single hit. By the time I've hit level 50, I can tank up to three hits without the assistance of chems or armor. At level one, I lack any weaponry designed to take out a deathclaw, so it'd be unwise to fight one. By level 50, I'm wielding plenty of guns that can kill a deathclaw in a single shot. See that? That's progression. That means things are different, that means the game is changing and providing me with new, fresh content to explore and enjoy as I play it.
Medium armor being removed =/= it's worthless. Medium armor being removed = Bethesda can't be assed to balance it.
I am hereby convinced you haven't even played New Vegas. Or you are currently severely intoxicated. You even go on to argue Skyrim's DLCs aren't doing the exact same thing. It's insane to me that you're sitting here comparing New Vegas to an MMO-style game and complaining about it's level-scaled enemies, all while simultaneously defending two games that offer nothing but MMO-style gameplay and level-scaled enemies. Seriously, it's the EXACT same mechanic.
Really, I'm speechless. I'm absolutely speechless. I would love to hear you explain what makes a New Vegas DLC so different from Skyrim or FO3, or what about them is "MMO-style." As for enemies being stronger in Lonesome Road and "why," all the enemies encountered thrive in irradiated settings. Guess where you are.
The only conclusion I can draw from every point you've made is that you do not like your games to be challenging. You've both implied that there's nothing wrong with being stupidly strong to the point you can't feasibly die at the end of the game, and you've criticized New Vegas while praising Skyrim in a situation where the two followed the EXACT same god damned formula, the only difference being that Skyrim's DR system means you'll never die no matter what gets thrown at you, whereas New Vegas' provides more damaging enemies that demand more planning and aim.
Seriously, are you intoxicated...? Not two posts ago, you argued "no damage immunity should ever exist. That's bad game design." Here you are now, showing how because a 10mm will kill both a light armor and power armor foe at the same rate if both activate the 20% bleedthrough, that's bad game design? Do you not realize that you're changing your argument, being a hypocrite or attempting to have your cake and eat it too? You cannot have it both ways.
Your cited math also fails to get the point: Look at the amount of hits you can survive with DT, then look at the amount of hits you can survive with DR. Notice anything? I do. The DT system means the higher-grade weaponry is killing you in ~5 hits or less. The DR system means the higher-grade weaponry still needs 10+ hits to kill you.
Please list for us all the occassions where you've played a game where an enemy needed 10+ hits to kill you, and you died and thought "DAMN I DIED, THAT WAS HARD, NOTHING I COULD'VE DONE."
It's too slow. It's too slow for anyone with half a brain to realistically die. I mean let's put things in perspective here: the total amount of hits you can survive as a power armor'ed character using DT is equal to the gap between light armor and heavy armor in a DR system. The TOTAL survived hits is a mere fraction and a mere statistic under a DR system! That's ridiculous! Do you not see how this is a problem? How the scale is simply too big and how now gameplay is far too slow for the player to die?
Furthermore, there is no 1.33 hits. It rounds up. This means that Power Armor in New Vegas allows you to tank 2 more hits from an AMR than Light armor. Is this a meaningful gap? Absolutely. A headshot counts as two hits thanks to a x2 damage multiplier. If you get headshot twice in a row by an AMR and you're in Light armor? You're dead. Before you even really get a chance to possibly react (depends on what you're doing), you could be dead. Three headshots though? You're going to have time to react. The power armor can save your life.
Honestly, if you sincerely believe that power armor allowing you to survive 10 hits (aka 11 shots needed before you die) is neccesary, I suddenly understand which demographic all these streamlined games keep getting sold to. 11 hits. 11. That is enough shots that the AMR guy - the guy with the big honking sniper rifle that fires slow as hell - will need to stop to reload before continuing to shoot you in the face. And this assumes he lands every shot. It also means that even in hardcoe mode, the healing-over-time effect from stimpacks will easily exceed his damage output. (they max at 15 HP per second, though a perk and Arcade as a companion can increase that further) And keep in mind, we are citing the most damaging gun in the game. It only goes downhill from there, with only a couple DPS-focused weaponry possibly providing a slightly larger threat. The best weapon in the game on DPS is only going to provide a damage output of 78 damage per second, but this is a weapon never wielded by enemies, and again stimpacks will negate the vast majority of the damage, and AGAIN it's far too long for your character to feasibly die.
You cannot die. The game is holding your hand. That's exactly what a pure DR system is. That is not a real challenge or threat, that is an illusion the game is feeding you to try and make you feel amazing. That you fail to see through that smoke and mirrors, that is what's truly amazing to me.