D&D 5E Few questions on how to build a Samurai for this edition

[DiscRover55]

1- By a strict reading, it doesn't seem to, but I would allow it. Ask your GM. It seems that the main use of Versatile is to fight like you were using a two handed weapon, but get that hand free when you need to cast a spell. At least, that's why they did it with the staff for the wizard, so I feel like that's something to keep in mind. That flexibility is why I have no qualms with using a FS to get near heavy weapon damage (plus, no bonus action attack).

2- Alert for Initiative bonus. Lucky is nice all around. Martial Adapt for another Superiority Dice. I've never tried a Charge build before, but could be interesting with a samurai. Heavy Armor Mastery is awesome if you're going that route. Resistant for another one of the "strong" saves - Dex or Wis. I actually really enjoy using Sentinel myself.

Personally, I would use either one of the defensive feats (Heavy Armor Mastery or Resistant), or go with Magic Initiate (if going Eldritch Knight) or Martial Adapt (if Battlemaster) for a bit of forwards preparation.

I went with Sentinel. Thanks for the advice! I mean it's one of the best choices to pick if I choose not to wield a Nodachi great sword

 

[Sword of Spirit]

Maybe because you calculated with 95% normal hits and 5% criticals. (Yes you did, got to the same wrong numbers with that wrong assumption)
In any scenario on average you hit with a 8+ or so...
Which make your critical hit rate something higher than 5%, because the conditional probability P(Crit|Hit)=P(Crit)/P(hit). So if you only hit 50% of the time, 10% of your hits are critical, not 5%

The average damage per attack (not hit), which is the interesting number, is only 3.75 without critical hits accounted for and about 4.0 with critical hits accounted for.
What I did not factor in are bonuses from strength. I must think about it, if it has an influence at all on the shape of the distribution, or if it is only a shift to higher numbers.

If you hit on 10+ it is 55%=0.55 hits, 5%=0,05 crit, so you average damage per hit (since you like that number more) is 8 for 1d10 longsword + duelist style, and 8 for the greataxe. (and still 4.4 damage per attack for both).
(In reality, you hit a little more often, leaving the longsword slightly better on average... 0.0X damage slightly)


So for the OP:
no problem in allowing a versatile weapon to be wielded in 2 hands and still benefit from duelist style. It won´t devalue the greataxe.

Ah yes, I did make that mistake. The funny thing is that I've actually done this sort of thing correctly before, lol.

 

[mlund]

1-Now, for the Dueling Fighting Style a Fighter can pick, can that +2 damage bonus apply a versatile weapon? Or is it restricted to only one hand, one weapon?

You can get the +2 damage bonus if you are "wielding a melee weapon in one hand and no other weapons" (PHB 72). That's fine with a longsword, but it means you aren't wielding the weapon in two hands, so you use the base damage, not the parenthetical damage entry next to the Versatile property.

In contrast, on that same page the Great Weapon Fighting fighting style triggers its ability, "for an attack you make with a melee weapon that you are wielding with two hands," and calls out wielding a weapon with the two-handed or versatile properties.

2-Assuming the DM allows the Human variant trait, I will be using it for my character. What feat would be the most worth picking up? I have my eyes on Great Weapon Master but, since a Long sword isn't a heavy weapon, I can't apply the "Power Attack" bonus to it so that sort of sucks.

None of the PHB feats have any optimal synergy with the longsword as a stand alone weapon. You can't use Defensive Duelist, Dual Wielder, Polearm Master, or Shield Master. Great Weapon Master is still solid, but as you noted you miss out of one of the feature. Savage Attacker, Lucky, Sentinel, and Martial Adept all give you an attack boost regardless of the weapon you wield.

Most of the feat specialties are appropriate for Samurai, though: melee attacks with a katana aren't the Samurai's bread and butter in an adventuring or wartime scenario. The battlefield is very different than a formal duel. In a battle the katana served as a badge, a back-up weapon, and the mean for collecting the heads of noteworthy opponents. In a war the Samurai made most of his kills using his best specialty among the other traditional weapons of the samurai - the great bow (daikyu), the glaive (naginata), or the great sword (no-dachi). There are fighting styles and feat options for each of these specialties and even the odd-ball who fights with both blades of his Daisho, but there's no similar specific support for a katana specialist.

Besides, what self respecting Samurai would want to risk his soul and sacred honor brawling with a rust monster or some acidic ooze pile? What kind of man sullies his grandfather's blade with the blood of bakemono? That's simply not how things are done in civilized society.

But if you have to be a barbarian about it and hit everything that crosses your path with your katana ... I suppose Martial Adept with Dueling Style and Battle Master will make your character distinctive enough from the alternatives. He'll have a significantly bigger bucket of butt-kicking maneuvers and superiority dice to use than another Battle Master Fighter - especially at the first half of his career. You even open up Maneuvers 2 levels ahead of any other Fighter, so maybe your character could be considered a Kensai ("Sword Saint").

Marty Lud

 

[UngeheuerLich]

Ah yes, I did make that mistake. The funny thing is that I've actually done this sort of thing correctly before, lol.

Actually I always believed the longsword was doing more damage than the great sword... I didn´t bother calculating it until I saw your post. And I was really surprised, that for hitting on 10+ it gave me the exact same number...

All in all the greataxe is just not a very good weapon for the fighter who tries to do reliable damage, and instead more a weapon for a barbarian.