I was recently surfing through the Monk subclasses and stumbled upon Way of the Long Death. It's definitely one of the better Monk subclasses, and the level one ability "Touch of Death" is amazing. Each time you reduce a creature to 0 hp you gain a number of temporary HP equal to your Wisdom Modifier + Monk Level. So i realized that a Half Orc Way of the Long Death is absolutely amazing at tanking post Tasha's Cauldron of everything. You prioritize Constitution and Wisdom and have now fixed a common problem with Monk's, surviving  close quarter combat. Any thoughts on this build?

I'm not sure what your deciding in Tasha's makes this so much better. The reality is that The Long Death has been a good but mostly ignored subtype all along. Some don't like the flavor. Others occasionally malign other details of it or didn't like that it's ultimate move costs more ki than quivering palm but it's always been pretty solid as monk sub classes go.  The Wisdom is actually the most important factor to Long Death Monks as a whole though and probably should be prioritized first and Dexterity second and maybe that's a bit of the issue people have had with it as well because not all understand, advocate, and/or play with that kind of style instead getting heavily focused on dex.  But Con is a good stat to pay attention to for all monks after their Primary (wis or Dex) or perhaps after both depending on a few factors.

Oh sorry I should have made that clear. In Tasha you can exchange any racial modifiers and by playing a half orc you typically get plus 2 STR and plus 1 CON. Post Tasha you could swap that out for plus 2 CON and plus 1 WIS, and with half orc's Relentless Endurance you could play a tank of a Monk with way of the long death. With savage critical you could be bashing in enemies in close combat, and constantly replenishing your hp, and in the rare instance you drop to or below 0 HP you could choose to drop to 1 HP with relentless endurance. What I was trying to say is that a Half Orc Way of the Long Death Monk post tasha is a really good tank.

You still need to reduce enemies to 0 before you get those temps, and your primary method of reducing enemies to 0 is by punching, which requires DEX. This subclass needs DEX just as much as any of the others. But yeah, an Orc Long Death Monk could be pretty tough, although I could see a lot of complaining every time a party member takes out your target and thus robs you of your temps.

That's why I thought it's good post tasha, because you could use the variant ability score improvements to swap out plus 2 STR to plus 2 DEX, making you both a major DPS and Tank.

I don't know how Orc has to be a thing, in fact post TCoE, Half Elf would be an excellent choice for a +2 and 2x +1 to move around, but ultimately everyone can end up with a nice Wisdom now, not just Orc? But you could get a +2 to Wis before TCoE with some races so it's not like TCoE makes the subclass better, just character options/choices better.

The idea of a Half-Orc bruiser who will just not die appeals to me. I'd put the +2 in dex and the +1 in wis though. 8/16/14/10/16/10

"I can do this all day."

ok. I've come back to this. I'll just say that having your tanking ability revolve around the death of enemies is problematic in the end no matter how well you build for it.  Because it' means it's not going to be functional at the start of combat when tanking is not needed the most and it's going to fail you in certain situations like Going toe to toe with that BBEG that hits like a truck because you can't keep such effects going.

So it sounds great on paper and it can be used for In the Moment Tanking or as an off tank to deal with the small or additional threats an encounter might offer. But it's not full tanking.

There is a similar problem, particularly in 5e where unless you are very lucky (kind of like Tallesin's Golden Snitch on Critical Role) you cannot rely on Critical hit effects to be the bulk of what you do either.  We just don't have a lot that improves your crit threat range and many of them are basically impossible to get on a monk.  And this is coming from somebody who has made a Kobold monk and actually gets advantage on attack rolls quite regularly.

Now none of this isn't to say that Long Death isn't Strong. It's always been a strong but fairly ignored monk Candidate sadly but it's competing against other flashier subclasses.  But i do at least like the attempts because long Death one is a subclass that deserves perhaps a bit more attention than it gets.

I think it's ignored because it's actually not that strong. It's kind of a mess.

Level 3 feature can a lot of temps, but you have to land the killing blow. Anyone who's played this kind of mechanic knows that it's kind of annoying trying to ensure a particular person lands the killing blow. And as mentioned above, when it does actually work you're most likely to get the temps when you're least likely to need them.

Level 6 feature is actually pretty unique - unlimited AOE frighten. There may be builds that could put this to good use as it's a nice support ability.

Level 9 you can avoid dropping to 0 hp. These "avoiding death" type of abilities are nice but honestly if you're getting a lot of use out of it then something's wrong.

Level 17 when you factor in the various tradeoffs, is basically a worse version of Quivering Palm. Feels tacked on like they had to meet a deadline and couldn't think of something new.

So you have a tank feature, a support feature, a kind-of-tank feature, and a damage feature. It's just all over the place. The only features that kind of work together are the tanky ones, but those are the most situational of the lot. Level 6 feature is pretty good but no other features synergize with it and you could argue that it directly conflicts with the tanky features. And the damage feature is uninspired and comes in very late. Furthermore, none of them feel very "monkish." You could put those same features on a Paladin or a Barbarian or a Warlock subclass without changing a thing about them.

Same thing goes for the flavor. Gains strength from killing things. Scary. Cheats death and does necrotic damage. These themes overlap pretty heavily with other classes who have subclasses that offer the same thing with a better overall package. And even if you're locked into monk, Shadow monks are better for the "spooky monk" archetype because their features actually compliment other monk strengths such as mobility and flexible targeting.

After really looking at it and thinking about how it would play, I think it's ignored because it's just not that good. I think its best use is probably to get to level 6 and then jump into another class that can leverage that frighten ability to the fullest.

a monk can actually make good use of the frighten ability. Primarily because they tend to be faster than the things that are going to be frightened and it's a way to deal with threats and make them back off so that hits aren't taken as well so it does work for the tank as well. Tanks that can make the enemy run away are doing the job in a different way as long as your smart about it.  Mastery of Death can also potentially be used a lot more than most other abilities like it. Though I agree that perhaps your doing something wrong if your making too much use of it. But at the same time it can preserve action order a bit better if you are tanking and potentially getting yoyo'd. At least until your Ki runs out.

As for the capstone. It's really not worse than Quivering Palm. It's about equivilant because it doesn't have some of the restrictions of quivering palm but in trade it's damage is more variable.  Quivering Palm takes up two actions to make use of where as Touch of Long Death only takes one to use. They have the same kind of saving throw to resist but Long death is potentially capable of more damage.  Enough to potentially kill some things anyway or equal the damage of Quivering Palm on a failed save. Long Death also doesn't rely on an attack roll to set up and be useful either which can potentially make it a bit more subtle in it's usage.  Quivering Palm's advantage is that you could hold it's potential over your targets head for some role play factor and it's a bit cheaper to use, but at the same time it's hard to affect multiple targets with in any quick order like the Long Death can be done.  There are a lot of ways that either one can be preferable for any given situation depending on what your trying to do.

Though when it comes to the third level ability. I agree that it is lackluster. Particularly in practice as compared to white room theory crafting.  It's very easy not to get that killing blow unfortunately unless your going out of your way to steal the killing hits from other players by various means.  But I didn't say it was key to making the subclass work either.

As for flavor. There is a lot of flavor in a lot of subclasses that could be easily pretty much straight ported over to other classes with little changes at all to how things work. Shadow Monk is a fine example of that as well.  The Flavor of it could be used by lots of classes and is even repeated in a couple of them such as the Sorcerer.  The mechanics might need slight altering to fit some of them but considering they are so low cost anyway switching them over to more of an action economy system or a "x" uses per rest system would not change them overly much.  So if we're going to be holding that against things we might as well pretty much throw a lot of things out and just start over.