The fastest way to get high runes in Diablo II Single Player is considered to be Lower Kurast running. You reroll your map until you get a map with 6 Superchests close to your Lower Kurast Waypoint. There are always 3 Superchests and a corpse next to a bonfire in lower kurast and I always wondered if it is worth it to invest the extra time to check the guaranteed corpse. It probably just takes around 2 seconds per run, but when doing hundereds or even thousands of runs it makes a big difference, when a run takes around 15-20 seconds.
That beeing said, I have seen people on YouTube drop the desired Ber-Rune and I myself dropped it from a corpse before. But although the odds of the superchests are clear (~ 2 / 65k) I am not sure about the odds of the corpses. Following up that question: there are many other popables in Lower Kurast. Is it worth to check those if they are on your path to the superchests?
Unfortunately, the wikis don’t show much information beyond a physical description of what the corpse containers are, and what they do:
Dead bodies are a type of container holding potential treasure. […] Clicking a dead body will move it slightly and reveal any items or gold that was hidden on it.
Corpses: The bodies of fallen warriors often litter the areas you traverse, and can be searched for loot.
The only list of chance to drop specific items from a container I have found is this one. Again, there is no evidence that this list is linked to corpses, but it does not specify anything beyond “Chests” or “Locked Chests”; though it does specify the “No Drop %” varies for different containers. Take that as you may.
According to this list, the chance of a Chest dropping a Rune is a 4.8% chance that it will be “good” loot, and another 10.8% chance that loot will be a rune; however this has up to 4 chances to drop this (if I’m reading this correctly).
At this point, this is the only information I have been able to find to support any hard values regarding a chance for a corpse to drop any specific loot, so I don’t think there is any hard answer for this yet, without some more specific testing.