It might should be harder to make a fine stone ring than a fine stone mug, but that's away from the idea here that seems to me to be hazardous to gameplay.
The critical fumble. "You drop your gun, it discharges and kills a kind, little, old lady, on the other side of the street." is all well and good if you're playing Bribe(the system the critical fail came from). However, this is Dwarf Fortress, and being able to run a prolonged single player campaign is more important than creating memorable critical fail moments around the table.
Look at the way DF handles critical hits. They're partially debilitating, and gruesome, but they aren't always an instant win, and they are usually required to make some level of sense. You can't punch a dragon's head off of her neck like a tee ball.
Failure should run the same way. It should be the mundane sort of failure, where you completely fail to strike the target, or you fail to create a masterpiece. --Not the sort of failure where your engraving is so bad that it destroys the wall.
Slipping and falling on slippery things makes sense, it happens all the time. That's why they make those caution triangles. Standing on a muddy ledge, in a rainstorm, is not particularly wise, but walking along on under the same conditions should be more than simply possible, but feasable.
Now mark, I'm an old mountain goat, from the snowcapped Rockies, so I have certain expectations about how well a person, or at least a mountain dwarf, should be able to handle themselves on a ledge. However, I don't think slipping on dry ground and sliding off a cliff is normal for any sort of adventurer.
Rhetorical Posit: When was the last time you fell down? What were you standing on? Is this more probable than punching off a dragon's head?