I'm sure that the 5e version will be watered down compared to the original module.
I'm not a huge fan of the original
Tomb of Horrors because I find it cheap and unfair. But, at the same time, I hope they don't defang it too much otherwise it loses what makes it interesting and special. Without the lethality there's less that makes the
Tomb of Horrors interesting: no unique funhouse puzzles or chambers, no memorable NPCs, and no interesting combat encounters. A
Tomb of Horrors where you don't get crushed, burned alive, annihilated, or starve naked in a pit just isn't a
Tomb of Horrors.
Plus, to some extent, people *want* to die in the
Tomb of Horrors. If it's too easy then there's no feeling of success or accomplishment. It's going to climb Everest and finding someone installed an escalator.
Hence my solving the Gordian Knot neither by making it less lethal nor playing it straight, but instead by making death sting less. (And sometimes encouraging you to find ways of dying.)
That said, there's a lot of places where the solutions to "puzzles" could be more obvious. Where a subtle clue is needed or the solution can be that little less specific. So figuring out the way past is more a result of figuring out the solution rather than brute force problem solving where you try everything until you get lucky. That's less interesting as there's no "eureka" moment prior to solving the problem or post-revelation scene where you go "ohhhh, it makes sense now".
I think this is where
White Plume Mountain is the stronger. It presents the wacky funhouse dungeon chambers and you just have to think of a solution. There's no singular solution and the problem is obvious. In the
Tomb of Horrors neither the problem nor the solution is obvious and often isn't logical. There's less cause-and-effect.
The only possible downside, is that because the adventure is pretty long, repeating the parts you've already done successfully in previous run can become tedious, so some fast-forward mechanisms can be employed. But at the same time, it would make a lot of sense to re-do the combats or anything that depends on chance (because different dice rolls can yield different outcomes). In the best case, you can end up with each re-run being different from the previous (thus adding some tension and excitement), but overall getting a sense that you are really advancing towards victory.
Replaying some bits would be super fast. If they know where to look, success is guaranteed. At that point, you can just fast forward through the intervening sections. "We go to the middle door, pull the 3rd level, duck, go through the hidden hatch behind the altar, tell the guard we'll bring him a bottle of red wine, and then climb the ladder."
To me, the extra interesting potential of this kind of story occurs when something bad happens and only half the party dies. And then the other half can either kill themselves or look ahead, being needlessly reckless because it doesn't matter. That and the fun potential of "Well, it doesn't matter if we die. Let's try X just to see what happens." It's a licence to get creative.
I imagine most combats could be run a couple times. Once when it's a surprise and a second time when the players know where it is and when it's going to attack (so they can ready an ambush or the like). After that, when they "reset" the combat just occurs again as it happened previously. They're just assumed to succeed, taking as much damage and using as many resources.
Or they can opt to run it a third time if they believe they can do it better or have a more efficient strategy, possibly gaining advantage on all rolls to reflect their knowledge of when and where to strike and when to dodge.
After all, in those types of stores, the heroes become super good at solving the known problems. That's represented by not need to roll. There's no longer any random chance.
In terms of experience, the party should get full experience the first couple times. When you're trying a fight again in a different way it's a different fight so your character can still learn something (and gain more experience). Which, of course, should be retained despite resets. (Although levelling shouldn't be permitted.) After the second time, experience should be halved for the third attempt at a fight. The character learns less. And there's less danger and thus there should be less of a reward. (And, from a meta standpoint, you don't want to encourage "grinding".) From then on there should be no experience gained: at that point, the reward of completing the encounter aren't experience but beating the fight in a better state (more HP, fewer spent spells, etc).
It was just a dream and a do over......... Sorry but that idea was in use before "Groundhog day". And I rather be in a party with a TPK. I will pass on the idea.
Using it as a method of negating a TPK is just one hook. You can run with the Groundhod/Repeat concept just fine without that.
The point is making the
Tomb of Horrors fun without either making it less lethal, making your players feel slighted, or having the game be slow as the group is painfully cautious and hesitant to try anything.
