The Kensei Conundrum

In my West Marches game, I've currently got a rule set (BECMI based, but with bits and pieces from other editions that I like) that includes both "western" and "eastern" character class options. One of those is the Fighter subclass Kensei. 

Now, anyone who has downloaded Flying Swordsmen or purchased Chanbara will know that this is an archetype in both. It's a warrior dedicated to the mastery of a single weapon (most often the sword, but not necessarily). The class first appeared in Oriental Adventures 1E, and I'm pretty sure it was a kit in 2E (don't have the Complete Fighter Handbook handy at the moment), was in the 3E OA, and even has had versions in 4E and 5E (where it's a Monk subclass instead of an alternate Fighter). 

I like the kensei concept a lot. A dedicated warrior trying to master just one form of combat. A duelist. A student of that one weapon. But the version (called Kensai) in 1E OA is full of fiddly mechanics and restrictions so it's hard to play. I know, I'm playing one in one of the AD&D PbP games I participate in. 

Seiji Miyaguchi as Kyuzo in Seven Samurai, Kensei

Jeremy has been playing my version of the Kensei in my West Marches game, and we've been discussing it. I want the mechanics to be simple and streamlined. Not too many bonuses, and also not too many restrictions. The problem Jeremy has is that this means it's not all that distinct from a regular Fighter. 

My Fighter looks like this: 

Level 1: Parry (1/day, any one attack that hits does 0 damage; taken from Stars Without Number)

Level 2: Sweep (Against creatures with 1HD or less, get 1 attack per level; taken from OD&D/AD&D)

Level 4: Combat Style (choose from a list of 7 feats, some subclasses have limited selections; various inspirations)

Level 8: 2 Attacks (Against creatures with 2HD or more; from BECMI Companion but simplified)

Level 9: Smash (-5 to hit but add Strength score to damage, but this is the only attack for the round; from BECMI Companion)

Level 12: 3 Attacks (Against creatures with 2HD or more; from BECMI Companion but simplified)

My optional subclasses are Cavalier, Kensei, Martial Artist, Ranger. 

The Kensei, in this version, has a limit on weapons and armor. They are only proficient with 3 weapons of their choice, at least 1 melee and 1 ranged. They are not proficient with armor, but may give up a weapon choice to take shields. I don't want to punish a kensei who ends up in a situation where they must use a weapon besides their specialized weapon (such as a battle of ranged weapons across a ravine) with either sitting it out or getting 1/2 XP the way AD&D does. 

Instead of armor, the Kensei uses their Dex score as base AC, and adds their BAB (I use ascending AC) to that. Since they have a prerequisite of Dex 13 to take the subclass, they start with at least AC 14 (6 descending), AC 19 (1 descending) if they get lucky and roll an 18 Dex. I'm working on an alternate version for TSR-East that can't pick shields, and instead of Dex as base, gets a flat AC by level plus Dex adjustment based on the Martial Artist class I created.

One of the three weapons the kensei chooses gains weapon specialization (+1 to hit, +2 damage) from 1E Unearthed Arcana. No other Fighter type in my game gets this. This is what makes them "the best" with their chosen weapon in my version.

At 4th level, they can choose from Archery (Dex bonus to ranged damage), Cleave (free attack if an opponent drops, not during a sweep), Iaijutsu (+4 to hit, double damage on the first round of combat), or Pole Arm Master (if you have initiative for the round and hit, the opponent cannot attack you this round). Jeremy has chosen Iaijutsu, as has Don for his Lark (Fighter/Magic-User), and it hasn't seemed overpowered. There have been lots of fights where they can't use it because things start out ranged, and even with +4 to hit they don't always. Also, my TSR-East Marches is shifting things around again, so Cleave may be going away, but Dual Wield may be joining the list, after my discussions with Jeremy.

Finally, at 9th level, instead of Smash, the kensei gets Whirlwind Attack (from 1E OA). In melee, they can make one attack against each opponent within range. Jeremy and I have been discussing this, too. As I wrote it this way, it is probably too powerful in melee, but screws over ranged kensei. I suggested a few alternate ways to reword this, and a -5 penalty to hit as with smash attacks, on a single roll compared to the AC of each opponent. Also a variant of sweep for ranged attacks, up to 1 shot per level. But I may just scrap it and let them smash like other fighters, because as written it seems like something to use all the time which is not good game balance. 

In addition to suggesting allowing dual wielders (Miyamoto Musashi is of course the real world archetype most often associated with kensei and he used katana & wakizashi simultaneously), Jeremy has also suggested things like increased damage die, or a version of AD&D's Assassination Table instead of iaijutsu, or a 3E+ Monk style Flurry of Blows ability. 

I'm not too fond of any of these options. 

Increased damage die may sound good for his concept (Jeremy's PC specialized in hand axe, and he has an idea for a dagger kensei as well). But a pole arm guy getting a die bump on a 1d10 or 1d12 weapon (yes, I have one)? That might be a bit much for Classic D&D. I don't want to start down the hit point inflation path of WotC. 

Assassination in AD&D, at least the way I read it, is intended for solo play, and requires time and patience to set up that % chance of an instant kill. It isn't the sort of thing you do in the dungeon 5 seconds after finding out that there's a minotaur in the next chamber. Jeremy countered that it would be less powerful than a sleep spell, and a saving throw would make it harder to use on high HD monsters. True, but I don't necessarily equate the weapon master concept with a "one hit, one kill" Rokugan Crane Samurai vibe. Plus, that table is big and clunky. I'd rather have an easy mechanic that we can just remember without a chart lookup.

I'm not fond of Flurry of Blows, because I'm actually trying to limit the number of extra attacks floating around in my rules (one reason the Cleave special ability is going away). The more times a PC gets to attack normally, the less special the Sweep ability becomes. And again, without hit point inflation to worry about, characters don't NEED lots of extra attacks, except when facing lots of low level monsters. 

Maybe I just need to give them a small bonus to damage with their specialized weapon every few levels the way 1E OA does. Get rid of Whirlwind Attack. Maybe at high level they can Sweep against higher HD monsters (2HD, maybe 3HD?) instead of the scaling bonus? Maybe UA style double specialization (+3 to hit, +3 damage) at higher level? I'm not sure what would be the best way to balance them here.