Hiving off from the "Access to Races in a Campaign" thread derailment:
There's such a thing as too much information, or information a character in character would not necessarily have, and this is one. In the fog of war there's no way of knowing whether the next swing that gets by your defenses is going to produce a small nick (4 points damage) or stove your head in (50 points damage); just like there's no way of knowing what your own successful attacks will actually accomplish.
It's along the same lines of a character in-character knowing its turn in the initiative order - an equally outlandish concept solved by rerolling initiatives each round.
Might not have been the best example of something "outlandish" for a character to know. I also don't think it's really such a huge thing to have static damage--you still never know if a blow is going to land, and before the first blow you don't know how much damage it will deal. Also, "fog of war" might not have been the best choice either--that's supposed to reflect the "you don't know specifically what's happening at every point on the battlefield"...which, in most games I've played, you
do know what's going on at every point on the battle map if you're using one. Only Roll20's computerized line-of-sight stuff has actually tackled that...and the DM found it such an enormous headache (because *he* can't see what ranges *we're* able to see, natch) that he basically handwaved it because it made his life too complicated.
Lan-"wondering both what monster does 13-68 points on a hit and what set of dice one rolls to get that range"-efan
Others have given some...weird and outlandish sets, but a simple 5d12+8 will do the trick. Just played around for a minute or two in AnyDice.
Though that actually demonstrates an important reason why "random" damage really isn't as meaningfully swingy as you'd like. You have less than a 10% chance (~9.3%) to roll any number outside 28-53 (a 26-point range), and you'll get a number between 33 and 48 about twice as often as anything outside that range (a 16-point range). Or, now that I've read more of the thread, if we use the stated damage value (11d6+2), we get an even
more centralized bell. The 95% confidence interval is approximately 31-50 (a 20-point range), and the 66% CI is approximately 35-46 (12-point range). When you then factor in the effect of rolling that damage more than once, the results will regress toward the mean (40.5 damage) per hit.
Ironically, it is for the creatures with the smallest damage attacks (single dice) that rolled damage leads to the greatest player uncertainty. For big bosses, rolled damage actually results in nearly as good of information as static does--there's always the small chance you're wrong, but again, regression toward the mean says that such outlier results should, well,
actually be outliers. Edit: And this is even more true if you roll your monster damage dice openly. Pretty much anybody with a head for figures who pays attention to (1) how many dice, of what size, you rolled and (2) the amount of damage you called out, can get a good estimate of the average damage and damage range of that monster. And while I don't do much OSR-style stuff...I can't imagine that most groups would be super okay with the DM always rolling damage dice behind the screen.