The problem is that you end up in this weird place where a master thief can trigger a pit trap, flub the save, fall 50 feet and survive every time, and the solution to that is to make the pit deeper because you are dealing with a higher level character.
To continue on with your mobster/fbi theme, they would be adding more explosives to a trap to ensure that it could kill more skilled opponents. It's odd.
I guess perhaps the way to handle it would be to change the fiction to match the abstraction: in the pit trap example, a character who survives the 50ft fall didn't actually fall - you evaluate the damage, apply it, then describe the character as hanging off a ledge or whatnot.
In the explosive example, the character throws himself out of the way at the last second, and the more deadly trap is actually getting more coverage or detonating faster.
Yeah, but in D&D, you literally need a more damaging weapon to kill someone who is more skilled at safe cracking. Suddenly flinging a fireball isn't enough - you have to sling abi-dalzim's horrid wilting instead.
I think I follow what you're saying. But in D&D somebody more accomplished in safe-cracking is more likely to be better prepared to avoid the consequences of failure. They kind of go hand-in-hand.
It's not a problem in our campaign since we don't use the old D&D falling damage approach. Falls cause some damage, but they also usually cause an injury, which now uses the exhaustion track in our campaign. The longer the fall, the more severe the injury is likely to be. Level 6 is death. Injuries use the death save mechanic, and you make one save per day, and requires 7th level magic to heal magically. So it's a long term effect in our campaign too. The math is designed to match the real-world math in that 50% of falls from 50 feet are fatal.
Lethal traps in our campaign either deal massive damage (also likely triggering a system shock check at the very least), cause injuries (bypassing hit points), are more likely to deal a critical hit (which also bypass hit points in our campaign), or use poison (also generally more deadly). Often a combination. While we don't technically have any 'save or die' effects, the possibility is there depending on your level, current state of health,
These are the current variation of rules I've been changing for 30 years, in part because I can't stand things like characters regularly falling long distances or jumping into fire, stuff like that. In essence, we want to ensure that the rules provide a mechanical reason that explains why nearly every creature in the world fears fire, to the point that many probably couldn't force themselves to run into a burning building to save a loved one. These are well known, so the players can treat circumstances appropriately. When attacked by a venomous snake, for example, the main suspense is in the first attack roll - to see whether it strikes high enough that it's over the boot (which is typically thick and stiff enough to protect against it), or if they are soft boots, then enough to penetrate. Most such attacks are a single attack and the snake slithers away, but the suspense is palpable because they know that the risk is extremely high...and painful. Because it's usually not a quick death, and more than one unprepared adventuring party has retreated as fast as possible to return to town where magic or an antitoxin might save the character.
But even with the core rules, the answer would be yes, you're going to have to go for a bit of overkill if your expected target is higher level creatures. Of course, you need to get pretty creative if your target is something other than human. So an especially potent poison with a DC of 25+. A fire or lightning spell of some sort cast at a higher level, pits that aren't only deeper but with spikes, poison, etc. Traps that require multiple saving throws, perhaps one that imposes disadvantage under certain circumstances, that sort of thing. So if the first part of the trap is a scything blade you can give the player an option of which way they jump if they succeed at their saving throw, left or right. Right is another trap, so they have disadvantage on their next save, and they have advantage on their save if they go left. A pit trap that has poison spikes, a self-closing lid, and fills with acid.
Most of the higher-level traps will involve magic of some sort, and it wouldn't be unusual for them to feature multiple damage types, perhaps something that restrains or traps the victim to make them more vulnerable, or what have you. The reality is, it's really, really easy to design brutally deadly traps (and if you have difficulty with that, go dig up some of the old
Grimtooth's Trap books for inspiration). It's somewhat harder to design those that target lower-level creatures. But I'm also not afraid to have traps that the PCs are able to just bypass. I just make sure they recognize the danger they would have posed, but it's their skills, level, or both, that allow them to avoid them.
Also, just a reminder that not all traps are designed to be lethal. The purpose of the trap should be considered too. Dropping them into a oubliette with an antimagic field, for example. Or dropping them onto a teleportation circle that sends them to one of 6 random locales, each with its own dangers (and probably alone). As I mentioned before, you can also design deadly traps that are less deadly than normal for some reason. My daughter and her friends fell victim to a collapsing walkway over a 1,500' sinkhole that would have automatically killed just about anybody (they were 3rd level I think), but a colony of giant spiders had strong their webbing across the chasm to catch things that fell into the hole. In this case, the PCs. It made the resulting encounter more interesting, since burning the webs would cause them to fall to their deaths. So you don't necessarily have to pull your punches in actual trap design, but you can find ways to mitigate the normal risk by current circumstances.
