Sigh, this is why examples and white room theorising gets so tiresome.
Why on earth does your fighter have a 17 AC? Good grief, you can do that at 1st level. Plate is AC 18 before you even start and you probably have that by about 5th level. AC 20 is not unreasonable for a fighter - Plate and Shield does make a pretty decent fighter. So, now we have our AC 15 rogue and our AC 20 fighter.
I think this does demonstrate a fundamental disconnect in the conversation. From my perspective, I would not expect a priori that a fighter would be wearing plate at all, unless he was going to open and eminent battle. If my fighter is going dungeon delving, just to pick a common example, I would be inclined to go with Breastplate (AC 14+Dex mod), both for the lightness and no disadvantage to stealth.
4e is taking a lot of hits in this thread, but I just see it as culmination of tendencies that grew out gamers approached the game, and how designers responded to that. A big one is the idea of specialization. Its beginnings are found in the creation of the Thief class, and later in Unearthed Arcana. Then it gained steam in 2e and really exploded in 3e. 4e's explicit, mechanically based roles are just a culmination of that design trend, an attempt to elegantly fix the imperfect expressions of the roles in 3e. So the essential play paradigm of those later editions was to Know Your Role and then relentlessly hone it. If you're a fighter, you are a defender (in 4e's elegant implementation) or a meat-shield (in 3e's less elegant one), so you're pumping AC, STR, and CON, as much as you can. And the game's design plays to this specialization. You can take a (pre-Slayer) fighter in 4e and turn him into a mobile striker, foregoing defending. But he's not going to be as effective as a class designed for striking (unless you
really have mastery of the system). But always have the highest AC you can, pump STR and CON, and wade into battle marking foes left and right, and you'll have lots of fun. It's a great feeling to have the DM throw 5 attacks at you and miss with 4. It's a great feeling to have the DM target one of your allies, and then you say, "I get an OA on that."
But. Look at
this AD&D PHB table. Only Fighters (and its subclasses) and Assassins can use any weapon. That includes longbows. Only Fighters, Assassins, Monks, and Druids can use spears. Only Fighters can use two-handed swords. Only Fighters can use longbows, spears, and two-handed swords
and wear heavy armor. So, if you were a Fighter in AD&D, you had your choice of armors -- study but light armors for dungeon and city adventures, heavy armor for when the crap was about to go down. They could set-up sustained fire of arrows from 210 yards away. When the enemy got closer they could keep them at bay with spears. When the enemy got to close melee range,
then they could go to their two-handed swords. That's not even getting into the vs. Type of Armor and vs. Size considerations. There are all these choices for what and how one might play a fighter. So I look at what Skip Williams rights about the fighter earlier in the thread, and it seems kinda off to me. He says, "In a fight, the party's sturdy brawlers generally are the first to attack the foe, usually by moving in and pinning down key foes with melee attacks." But I'm thinking of the Moldvay Basic example of combat, where the first thing the fighters (dwarf and elf) do is engage the enemy with ranged attacks.
For whatever reason, people said, "Forget all that," and tended to just specialize in one weapon (typically the sword), wear their heaviest armor all the time, and then just wade into battle saying, "I attack." Not surprisingly, this was found to be boring, so since 2e the designers at D&D have been looking at ways to make that highly specialized role interesting with various mechanical implementations -- kits, feats, marking, etc. I really enjoyed the 4e fighter for what it was -- and yet, why was the fighter's historical proficiency with ALL armors and ALL weapons given to the Paladin? Why did their ability to layeth the smack down from long distance go, for all intents and purposes, to the Ranger? When I played the 4e fighter as a defender, it was so sweet, but I missed that versatility.
And I think this holds true for just about all the classes. Healing starts as simply a minor part of the Cleric's skill set (complementing their combat and Turning Undead abilities), and eventually they end up as the Healbot, and 4e had to figure out how to make that fun. Thieves were the dungeon skill guys, light on combat ability but with an occasional damage spike, eventually they become the skill monkey with nothing to do in combat (sneak attack being nerfed beyond belief) in a game that was becoming more and more combat oriented, so 4e had to figure out how to make that workable. As for wizards, well...thread upon thread has hashed that out. Suffice to say, they started out as artillery (with a bit of utility), and eventually 4e had to figure out a way to fit them into a party dynamic without overpowering everyone else.
I can't blame 4e for the choices its designers made -- they had good reasons for doing so. All the same, I'm glad that 5e went with a less specialized approach. I like all-around, multi-role characters.