Zardnaar
Legend
Kind of a spin off of the Mearls boss monsters design thing. He has identified players are not playing as they assumed.
The 5MWD is a problem no version of D&D can really cope with. Its gotten bad since 4E and the removal of all the badwrongfun monster abilities that could challenge the PCs with only 1 or 2 encounters.
Recently I ran a Castles and Crusades game set in ancient Greece. Exploration heavy. The PCs at level 3 had to return home basically using random encounters with bandits.
Its a modern problem (post 3.0) ramped up since 4E and D&D becoming easy mode by default. Its not that hard in OSR games either but the differences are very noticeable. No the poisoned condition isn't that bad it's a bonus action level 2 spell to deal with. The 4E to 5.5 attrition as default model has failed entirely imho junk it the concept wont work at least at a price people will pay (combats that don't last 1 hour+).
A 6E rewrite would essentially have to reinvent D&D entirely. Probably gritty, removal of dailies entirely make it a 10 level game. Its a complete rebuild. I suspect such a game would tank harder than a T-72. Option B is make tougher monsters. Most of the required elements are in 5.5 but theyre scattered over multiple monsters and often high CR ones.
I don't think you need to bring back save or dies or energy drain but you can use new elements. Old school energy drain could become exhaustion levels. Save vs death or die becomes 2d6 or 3d6 damage per CR of a critter. A CR 8 assassin with poison would need to deal 16d6-24d6 damage. Hitting harder can have flow on effects however eg critical. Can modern players handle getting one shot (0 hp)on a critical? Should critical hits even exist?
5.5 has added a whole heap of low level wisdom save spells that disable opponents. Obvious offenders are command and tashas hideous laughter and very cheap twin spell on sorcerers. Other options include sleep and old favorites like hold person. If a 5.5 monster has a weak wisdom save its CR may as well be 0. The most efficient meta party would be 1-2 control types and 3 martial strikers. Best strikers tend to be dual wielding and great weapon builds with fighters and paladins level 11+ standing out. Spellcasters cant deal damage has enough at levels that matter using spells. Theory craft builds can at higher levels abusing CME errata or not.
So what abilities matter in 5.5? One creature the rakshasa has greater magic resistance. It shuts down all save or suck spells and anything using attack rolls. Higher CR critters sometimes have immunity to stunned, paralyzed and prone. That shuts down easy advantage gaining conditions. AC 18 is not effective level 10+. Hold monster spells start turning up as well. Paralyze something advantage to hit double damage. Monster wisdom saves tend to be lower. Even lower are monster intelligence saves. Tashas mindwhip your way through the MM. Twin it. D&D easy mode hit points don't matter.
Here's a sample creature from BG3. Generally you encounter it level 5 or 6.
On honor mode 450 hp and a boat load of immunities and resistancs. Vs level 6 PCs guess how long he lasts? Using BGisms 1 round. Without cheesing it using 5E stuff 2 rounds maybe 3 if you roll poorly. As I said the HP as attrition concept has failed entirely.
Once again BG3. Raphael and Cazador. Generally seen as the toughest monsters. Raphael has 666 hit points you encounter him level 10-12. This is more HP than any 5.5 monster at lower levels. He lasts 1 round if you use BGisms, 2 rounds if you play normally. Cazador might last 2 or 3 rounds but he's not going to be doing much.
Basically if you took the tougher 5.5 monsters and doubled or tripled their hit points its not going to matter they might survive an extra round or two. I've see higher level Champion fighters action surging 7 attacks a round multiple critss landing 150+ damage (BG3 you can do that in 1 hit). It wouldn't matter to much if you replaced the fighter with a Barbarian, Monks, Paladin or bladelock. You might gain a round maybe. These aren't particularly optimized characters either just using the obvious feats like great weapon master or the dual wield one+nick. 5-7 incoming attacks isn't hard to do. One PC is using basic +1,2,3 items as well so its not like theyre packing vicious weapons (2 in party only 1 being used).
Final thoughts if youre making DM specials or potential 6E. 5E saving throws and HP bloat suck and don't really work anyway. "Good" saves need to be around +7 with advantage or legendary saves 4 or 5 to resist basic leve 1 save or sucks. Greater Magic Resistance rocks but its only on 1monster. ACs need to creep up around 20-22 at least by level 10ish.
6E rewrite. The hit point bloat needs to go. Ideal HP imho old vs new probably needs to reduced to 3.0 or 3.5 levels. Damage needs to be scaled back. Saving throws need to scale universally OSR/4E. Magic resistance needs to be immunity if it works similar to 1E/2E, the 3.5 minis game or Greater Magic Resistance. Monsters need to have scary abilities again and overnight healing needs to go. Hell you could bring back scaling boom spells they haven't been a problem since 2E maybe 3.0.
This would give DMs the tools to challenge PCs doing 1-2 encounters. OSR can do it. But its flexible for 4 encounters or 6-8 depending on encounter design. Adding more immunities or greater magic resistance could also work but its really a band aid for wrong design decisions made in 4E onwards. It doesn't matter to much how you scale HP if youre scaling damage up as well. And we have seen what happens if you scale damage low and have buckets of HP. Both approaches are flawed.
The 5MWD is a problem no version of D&D can really cope with. Its gotten bad since 4E and the removal of all the badwrongfun monster abilities that could challenge the PCs with only 1 or 2 encounters.
Recently I ran a Castles and Crusades game set in ancient Greece. Exploration heavy. The PCs at level 3 had to return home basically using random encounters with bandits.
Its a modern problem (post 3.0) ramped up since 4E and D&D becoming easy mode by default. Its not that hard in OSR games either but the differences are very noticeable. No the poisoned condition isn't that bad it's a bonus action level 2 spell to deal with. The 4E to 5.5 attrition as default model has failed entirely imho junk it the concept wont work at least at a price people will pay (combats that don't last 1 hour+).
A 6E rewrite would essentially have to reinvent D&D entirely. Probably gritty, removal of dailies entirely make it a 10 level game. Its a complete rebuild. I suspect such a game would tank harder than a T-72. Option B is make tougher monsters. Most of the required elements are in 5.5 but theyre scattered over multiple monsters and often high CR ones.
I don't think you need to bring back save or dies or energy drain but you can use new elements. Old school energy drain could become exhaustion levels. Save vs death or die becomes 2d6 or 3d6 damage per CR of a critter. A CR 8 assassin with poison would need to deal 16d6-24d6 damage. Hitting harder can have flow on effects however eg critical. Can modern players handle getting one shot (0 hp)on a critical? Should critical hits even exist?
5.5 has added a whole heap of low level wisdom save spells that disable opponents. Obvious offenders are command and tashas hideous laughter and very cheap twin spell on sorcerers. Other options include sleep and old favorites like hold person. If a 5.5 monster has a weak wisdom save its CR may as well be 0. The most efficient meta party would be 1-2 control types and 3 martial strikers. Best strikers tend to be dual wielding and great weapon builds with fighters and paladins level 11+ standing out. Spellcasters cant deal damage has enough at levels that matter using spells. Theory craft builds can at higher levels abusing CME errata or not.
So what abilities matter in 5.5? One creature the rakshasa has greater magic resistance. It shuts down all save or suck spells and anything using attack rolls. Higher CR critters sometimes have immunity to stunned, paralyzed and prone. That shuts down easy advantage gaining conditions. AC 18 is not effective level 10+. Hold monster spells start turning up as well. Paralyze something advantage to hit double damage. Monster wisdom saves tend to be lower. Even lower are monster intelligence saves. Tashas mindwhip your way through the MM. Twin it. D&D easy mode hit points don't matter.
Here's a sample creature from BG3. Generally you encounter it level 5 or 6.

Grym - bg3.wiki
Grym is a powerful Adamantine Golem that eternally protects The Adamantine Forge. It cannot be damaged without becoming superheated first.
bg3.wiki
On honor mode 450 hp and a boat load of immunities and resistancs. Vs level 6 PCs guess how long he lasts? Using BGisms 1 round. Without cheesing it using 5E stuff 2 rounds maybe 3 if you roll poorly. As I said the HP as attrition concept has failed entirely.
Once again BG3. Raphael and Cazador. Generally seen as the toughest monsters. Raphael has 666 hit points you encounter him level 10-12. This is more HP than any 5.5 monster at lower levels. He lasts 1 round if you use BGisms, 2 rounds if you play normally. Cazador might last 2 or 3 rounds but he's not going to be doing much.
Basically if you took the tougher 5.5 monsters and doubled or tripled their hit points its not going to matter they might survive an extra round or two. I've see higher level Champion fighters action surging 7 attacks a round multiple critss landing 150+ damage (BG3 you can do that in 1 hit). It wouldn't matter to much if you replaced the fighter with a Barbarian, Monks, Paladin or bladelock. You might gain a round maybe. These aren't particularly optimized characters either just using the obvious feats like great weapon master or the dual wield one+nick. 5-7 incoming attacks isn't hard to do. One PC is using basic +1,2,3 items as well so its not like theyre packing vicious weapons (2 in party only 1 being used).
Final thoughts if youre making DM specials or potential 6E. 5E saving throws and HP bloat suck and don't really work anyway. "Good" saves need to be around +7 with advantage or legendary saves 4 or 5 to resist basic leve 1 save or sucks. Greater Magic Resistance rocks but its only on 1monster. ACs need to creep up around 20-22 at least by level 10ish.
6E rewrite. The hit point bloat needs to go. Ideal HP imho old vs new probably needs to reduced to 3.0 or 3.5 levels. Damage needs to be scaled back. Saving throws need to scale universally OSR/4E. Magic resistance needs to be immunity if it works similar to 1E/2E, the 3.5 minis game or Greater Magic Resistance. Monsters need to have scary abilities again and overnight healing needs to go. Hell you could bring back scaling boom spells they haven't been a problem since 2E maybe 3.0.
This would give DMs the tools to challenge PCs doing 1-2 encounters. OSR can do it. But its flexible for 4 encounters or 6-8 depending on encounter design. Adding more immunities or greater magic resistance could also work but its really a band aid for wrong design decisions made in 4E onwards. It doesn't matter to much how you scale HP if youre scaling damage up as well. And we have seen what happens if you scale damage low and have buckets of HP. Both approaches are flawed.