Recent changes to fighters, in particular, the Second Wind ability have made them quite attractive for those looking for a melee experience. Second Wind, which heals you for 1/2 of your HPs (and amplifies on HAMP) and clears most ugly effects you might acquire (such as mummy rot) is better than Lay on Hands in every way personally (LoH does allow heals on party members which Second Wind does not) which means Fighter might be moving ahead of Paladin soon as a preferred class. On hardcore, this is the build I took to the favor cap. Season 7 has a favor cap of 3000 but this could easily get 5000 as well since once you get to those mid-levels you're almost impossible to kill on elite.
Starting Race and Stats
Purple Dragon Knight. Why? Well, you get a 32-pt build and an equipment package at L15 (more on that latter). Now, I wanted to try a traditional longsword and shield Vanguard. Longsword ends up with a 16-20 x4 profile. War Hammer is identical if you want to swing a hammer. This build is a tactical creation so if you want to strikethrough (and have 32-point veteran unlocked) I'd go Dwarf with Dwarven Ax. If you must swing a bastard sword, then any class will do.
For starting stats you want at least 16 STR 16 CON 13 DEX (for precision). I wanted 4 skill points (Jump, Balance/Swim alternate, UMD, Intimidate). I took 17 CON then but you could go STR or you could split INT and CHA. All level points into STR.
Feats and enhancements
We get a ton but end up using them all and still must make a tough choice or two.
1 - Precision, Shield Mastery, Weapon Focus Slashing
2 - Stunning Blow
3 - Improved Shield Bash
4 - Knight's Training. Did you know Fighters could get this so early?
6 - Weapon specialization slashing, Heavy armor combatant
8 - Improved shield mastery
9 - Improved critical slashing
10 - Tactical combatant
12 - Greater weapon focus slashing (need this for T4 Kensai), Heavy armor master
14 - Greater shield mastery
15 - Greater weapon specialization slashing
16 - Tactical supremacy (+9 to your DCs with the STR point)
18 - Heavy armor champion, Toughness (this could also be GR weapon focus slashing if you want 2 melee power but on HC toughness is better in my opinion. Could also take improved trip.
20 - Tactical mastery
On Enhancements, we are going tier 5 in Kensai and the 20 core in Vanguard. That means we have 41 and 33-35 APs tied up. That means you really don't have enough for Know the Angles trance, even with a +1 universal tome.
Equipment
This is always going to be hard to plan on for hardcore, but if you get lucky or are running this on live you'll benefit from Feywild and Ravenloft gear (The Best Defense is an amazing DPS shield but I couldn't pull despite ransack in Oath). I got lucky and pulled the Undying Sapphire from Isle of Dread giving me a deep unconscious range (didn't have to use it but still nice to have that cushion which is rather big - an extra 65, for elite). Another nice benefit to PDK is three equipment items are actually useful at L15 - Knight's Blade (vorpal!), Knight's Girdle (20 vitality +1 exceptional CON), Knight's Sabatons (25 Speed/and attack bonus, Dex 4, feather falling).
I farmed adamantine ore on casual at level 8 in Relic of a Sovereign Past. Difficult has no bearing on the ore drops. For example, I got 13 ores on casual. The Nightforged Avenger Blade is only 10. You can also sell these ores for a decent amount at the auction house. I did a lot of comparing between the Avenger Blade and the Barovian Longsword. Ultimately, I like the Barovian better even though the Avenger blade has an extra 2 crit range. It just depends on whether you want to rely on that big strike or the more sustained bonus effects the Barovian blade provides. The Knight's Blade outperforms both having vorpal and the highest base damage of the three. Running on elite any vorpal hit kills just about anything you face through Sharn and remember you're using this from L11 quests on.
How does it play?
Look, you're never going to outkill the Bard (who is the new FVS on hardcore), but the DPS is much better than you might think. Anything can be stunned will be stunned. And this is on a first-life character with no STR tomes. At level 16 you're over 800 Hps, 100+ PRR, 5-second winds, 60+ AC. You are almost always comfortable in quests. Traps aren't going to do much damage to you. Second wind bails you out of nearly any situation. Shield Rush is great allowing you to zoom forward into a pack of mobs hitting them all. You can then unleash your two stuns and a trip. You'll never be tops on the kill count but you won't be last either. Where you fit varies over the levels as I found the Vanguard swaying and declining then swaying again based on how other classes are picking up abilities. Once you start to get the enhanced attack speed from Vanguard the class is a ton of fun. You can wade into mobs like a Knight in a movie and just start thrashing things. I feel we finally have a playable classic armored knight with a longsword class.
Going Dwarf ax or Bastard sword will require you to take THF feats for strikethrough. With Knight's Training, Longsword has a better crit profile than bastard sword (although base damage is lower) so you're really building for strikethrough. That changes the build a lot as you'd need to drop 3 feats (4 effectively if going dwarf since you lose the bonus feat) for THF and you would be compelled to go into Fury epic destiny for the strikethrough there.
Into epics, the three EDs would be Dreadnought, Crusader, and Sentinal. Both Dreadnought and Crusader have cases to be made for primary depending on whether you want to enhance your shield or your tactics.
Conclusion
I saw a lot more fighters in hardcore during season 7. They seemed to finally reach a class attractiveness on equal footing with barbarians and paladins. I observed several Eldrich Knight builds in groups with my fighter and I always preferred my fighter. DPS is virtually equal and the Vanguard is a ton beefier. I'm not saying you can't build a good EK, with imbues, that is certainly possible, but the Vanguard fighter has so much going for it now - fun, comfort, reliability, defenses, a pleasant fighting style, and animation change to the THF swings we are all so used to by now. Give it a try, I believe you'll like what you find.