How much more risk do you need? Any risk at all. You are already taking that damage, and it's not a risk on a failed roll to take the damage you are already taking. Now, if you are volunteering extra damage on a failed roll for being out of position to defend against the attack, that's a risk.
The penalty is a less damaged or undamaged monster that is going to swing back. The reward is a more damaged monster that is closer to death, or possibly a dead monster that can't attack back.
I've been at tables with fumble charts.
Sorry, I thought we were talking about 5e D&D, not homebrew games. If you want to start bringing other games into this conversation, I'm all for it.
But, the point is, failure does not equal penalty. You ignored my example of the wager. Would you take the bet? Would you risk a hundred dollars on a d4 roll? On a 4, you get your money back, on a 1-3, you lose your 100 dollars, plus another hundred dollars.
Because, that's what you're asking me to do with the skill example. Why on earth would anyone take that bet? Well, actually, I know that people would take that bet becaue people are spectacularly bad at calculating risk vs reward. If you're going to give me a DC 25 check to avoid all damage, but, I take double damage on a fail, I either want that DC to be about 15 (which reasonable for the risk/reward) or you're going to have to give me a HELL of a lot more reward. No only do I not take damage, but, the fear of my spectacular landing causes all enemies who see me to flee in terror for the next thirty minutes. IOW, for that kind of risk, I better end the encounter in a win. For that kind of risk, I should become favored of a god of luck who will let me succeed the next three saving throws of my choice, as well as not taking any damage from this fall.
But a 1 in 4 chance of no damage vs 3 in 4 for double damage? That's just bad.
Again, since folks are defending this, I can totally see
@iserith's point that trusting the dice in a game is a VERY bad idea. Far, far better to try to find an approach (either leveraging spells, IMO, the most common approach or finding an applicable narration that obviates the need for a die roll).
Why are you saying it's the same hall when it's obviously examples of three different halls?
Sorry but it wasn't obvious to me. But, even if it was three different halls, why would the player come up with three different appoaches. Well, that got answered -
@Imaculata would telegraph the traps in each hallway and the player is expected to react appropriately. Again, not my cup of tea, but, hey, at least it makes sense.