Do later editions of D&D make smaller parties more viable?
I confess, I probably don't have enough experience with later editions (I have none with 5e) to answer this question accurately. Frankly, however, I don't see how the rule set actually matters where the problem is concerned - since everything that threatens a single character in the party can be increased or decreased in degree at the will of the dungeon master. What difference does it make that two characters have more hit points in this system rather than that? Or that those same characters are able to cause more damage in this system, or heal faster? Isn't it a question of how many monsters the party encounters? Or how high a height the character falls from? Isn't the x-factor the decision of the DM to throw this much, this quickly, in these circumstances and with this much determination?
No matter how many hit points a character has or how many surges, I can always stack the deck with another dozen creatures pouring from another doorway, without mercy. Which means that early editions of the game can be adjust the deadliness of encounters just as easily as any other edition - since the rule set doesn't limit the abundance of deadly possibilities. Yet I hear every now and then that earlier editions lead to more total party kills.
My guess would be that modules like Tomb of Horrors or The Hidden Shrine of Tamoachan built up a reputation for crunchy death-dealing sessioning, leading a lot of single-minded players into a mind-set that early gaming HAD to be deadly or else it wasn't 'D&D.' Execution-style dungeons were trash in their day, played mostly by tourists who were in love with the idea of murder, death and killing, the same way that a fascination for these things will roll around in an emo's mind while clothing themselves in another layer of black. Young boys develop such a fetish for the prospect of death that they'll dodge trains, jump from high bridges and otherwise experiment with chemicals just to prove that blood still flows in their veins. For a segment of the population, D&D offered a safe, catechistic means of proving one's commitment - "I am willing to throw away a hundred characters to order to finish this dungeon, because that is how much I love this game!"
Unfortunately, this built up a renown for idiocy among certain groups in the population, so that I am still running across non-players in the late forties and fifties who - having not heard a word about Dungeons & Dragons in thirty years - still feel the need to roll their eyes upon hearing the words, remembering as they must the fuckwits screaming about the amount of damage they took in their high school cafeterias. The impression was rooted and there it remains.
The question will arise, do I tailor the number of creatures to the party's size. Of course I do. Not in the sense that most would - if there is a goblin village in the area, then there is a goblin village. But a party of 18 characters and their henchmen would make enough noise in approaching such a village that the first encounter would probably be a mass attack directed at the party before they knew a village existed. On the other hand, two characters would make such a small footprint on the environment that they would probably stumble across the village undetected, thus allowing them to decide what to do about it.
The number of enemies is not the relevant issue - but the manner in which those enemies are encountered IS. The smaller the party, the more likely they will be able to 'cut out' a section of the enemy and deal with them on their own terms. If, however, two morons insist on openly approaching the enemy without thought given to strategy or tactics, then yes, they're going to die. Quickly.
My 'tailoring' of my world is based entirely on giving my players the heads up where it comes to danger. Knowledge is power. Survival is the wise implementation of that knowledge. If I as a DM were recalcitrant about delivering up that knowledge - and the possibility of players manipulating their situation into something they can handle - then yes, I probably would create a lot of TPK's. But I can't see how the rule system I'm using is relevant to the situation.
But then, my small experience with 4e suggests that DM's are unwilling to create truly massive combats in the game. No doubt, that is due to the ludicrous number of rules and sub-rules and rules of opportunity, all of which encourage situations of one party vs. one enemy, rather than a party fighting, say, 40+ enemies (which occurred in my last running). Given what I've seen of later editions, 40+ enemies becomes a hassle - but perhaps that is due to my limited experience. The reader should please correct me if, as a DM, they regularly run combats that feature squad or company sized battles.
For me, those may run half a session - but they're manageable and on the whole it usually means good treasure. 8 times out of 10, however, the players could avoid these fights - only the players like them. While TPK's will sometimes threaten, they rarely occur. In fact, I haven't had one in - fifteen years?
True enough, my parties have learned to run away. Even when half the party dies, the rest usually get a chance to escape. Partial Party Kill's are definitely the norm.