Ilbranteloth
Explorer
The British did come up with a plan to kill Hitler but abandoned it because it might actually prolong the war.
The encounter rules in 5E do not really work, a lot of CR 10-15 critters are really fore level 7-10 PCs. People have expectations of higher CR stuff due to 3E presumably but you probably want to assume a more 1E mentality where a Balor had 8+8 hit dice.
I noticed this back in 2014 but more or less got accused of playing the game wrong when I pointed it out on the forums.
A plan is different than execution, though. We'll never know if it would actually have worked. But somebody who commits suicide rather than surrender or admit defeat can't have been a very formidable in direct combat.
I'm less concerned with the actual Hit Dice as I am the purpose of the monster. If all a Balor is is a bag of hit points that can do some fire damage to you, and might drop a character or two to 0 hit points, then it's not really much of a monster. And if it's designed "to be a challenge" then the AC/HP/Resistances are a moving target based on your campaign and party.
To me, a meaningful design approach is to consider the world as a whole, and then design abilities around what people would find terrifying. For example, a lion should be capable of killing the average person with ease. That's 90%+ of the population. A Balor should be able to destroy a significant portion of an average town if it wanted to. As written, both of them meet that criteria.
The PCs aren't "the average person," they are the exception. So the rules need to determine how much better than the average person they can be, and when that exceptional ability isn't as important. That also sets a baseline for determining what creatures may or may not be dangerous to them. The CR system may very well be flawed, in particular with recommending a single monster against a party of 4, but I think that's in part because they look primarily at the potential damage output of the creature, and whether that can kill a single "average" character within two rounds. The expectation that the creature will last at least one round, and 50% of the time or so will gain two attack sequences if it wins initiative in the first round.
The problem I have with the system as a whole isn't the amount of damage they may or may not do, nor how many rounds they'll last. It's all about whether the players/characters will fear the monster. Because of the rules, dropping to 0 hit points isn't a big deal anymore (although it is in my campaign), and just damage alone, or the amount of hit points a creature does, isn't enough either. Save or Die effects definitely did the job in 1e, but I'm not a fan of that without a chance for survival either. So it's finding a middle ground. I've tweaked the dying rules, and I have a number of effects that utilize the exhaustion track (with differing recovery speeds).
So here's an example as to how my rules thinking works.
A lion has a good chance of knocking a target prone. Because the lion is a large creature, a medium or smaller creature has disadvantage on their saving throw to be knocked prone when a 400 lb lion jumps on you. Once knocked prone, the lion has advantage on its attacks. The only thing I added is that ff it scores a critical hit, it has locked on your throat and you are suffocating must make a DC 15 + number of rounds without air Constitution saving throw or fall unconscious).
This is all based on the way a lion actually attacks a person, and the fact that no matter how good a fighter you are, if there's a lion on top of you, you'd better do something quick (or even better, have help). It doesn't change the CR since it only occurs on a critical hit (and doesn't change the damage output).
It makes for a far more deadly campaign if they aren't careful. Of course, if you're wearing mail armor in my campaign, you have resistance to piercing weapons, and if you have throat protection, you'd have advantage on your saving throws to suffocate. So armor is something that is far more useful in my campaign. But most of my players would still fear a lion simply because it could still kill them quickly regardless of their hit points.
I'd also argue that my approach is probably not what most people would want for a published game. I know there's a group of people that do enjoy it, but it's not the right design for a mass market game.
Do I think a lion in 5e is too weak? Not necessarily. As it is, the ability to knock you prone increases its chance of hitting you, and as written it has a good chance of killing any 1st level character in the first round. Even 2nd or 3rd level characters are at risk in the first 2 to 3 rounds, especially if they are alone. What's lacking in all editions, in my opinion, is the fact that a lion represents thousands of years of evolution as a top predator. Their success rate hunting is far from 100%, but once they have their prey, it's an almost 100% kill rate - especially if the prey is smaller than them. Their primary tactic (like most/all big cats) is to attempt to lock onto their prey's throat to suffocate them, or break their spinal column. I wanted their tactics to reflect that. My tweak doesn't really alter it too much, but the possibility of it is enough - and it's even better if somebody falls victim to it, even once.
But game statistics like hit points aren't enough anymore to instill fear into most players. So I utilize wounds, injuries, energy drain, and other conditions that bypass the normal hit point pool for creatures that should be terrifying. The players know this going in, and they treat things with a lot more respect because of it. Does it happen often? No. But the effects are significant, sometimes long lasting, and difficult to eliminate (including through magic) and therefore make the players approach the monsters quite differently than a standard game. Combined with using intelligent tactics where appropriate, makes combats, when they happen, much more interesting.
You know what else I think should be horrifying and terrifying? Undead. While not all undead cause it, necrotic damage in my campaign cannot be healed by natural means. It requires 3rd level magic to heal. Which inspires a lot more respect for undead in my campaign. Because they can't tell if that walking corpse is "just" a zombie or a wight.
I'm not concerned necessarily in making combat last longer because it takes more hits to kill the monster. Combat lasts longer because the players and monsters might take time to address positioning on the battlefield, retreating, and searching for opportunities to gain advantage. It's not just the monster design that does this, though, as I noted armor works differently, I don't use combat rounds, all sorts of tweaks that work together.
This isn't new for me, I did it to AD&D, 2e, 3e, and even the little bit of 4e we played.
When I look at the 5e design as is, it's pretty consistent. It's designed to be less deadly. I see comments in threads that insist 0 hp is not dying, is just unconscious. That it's better to wait until somebody is at 0 hit points to heal them, then before. Complaints that monsters are too easy to kill, and that traps are not effective. That's by design. I don't know what figure they are shooting for, but I think there is an design approach that at least 60% of parties should be able to complete a given AP successfully. Possibly more. The risks of a high level monster lasting more than two or three rounds is pretty high. In most cases, somebody would likely die (well, be knocked unconscious at 0 hp). You regain everything each night during a rest, and gods forbid that you have to waste a spell slot on a utility spell. No, they are rituals now. It's not a question of one thing like solo monsters or BBEGs. The game is designed to be easier. I guess it's better than the revolving door of resurrection of 3e/3.5e, but not much.
But I also don't have any illusions that they are going to design more to my approach. Why? Because sales have pretty much shown that they have a successful design. That's not to say they won't change it, or modify things, since it's pretty clear that they are publishing a new variation of the ranger. And the new dying and resurrection rules that will be in ToA are, I think, in part a response to those that want things a bit more deadly. I'm interested in what other rules they might have, if any.