Turned off the weighted dice (which were on by default) and the game became quite nasty, to the point where it can take two or three turns for a party of 4 plus a summon to make a 60% hit.
Maybe the weighted dice are on by default to counteract something broken in the randomizer. Maybe it’s to help players get to the late game faster and lessen the feeling of burn out. In any case, weighted dice patch 8 far easier than before.
This is true. Back in patch 3 or 4 it was proven (using a sample of >500 dice rolls) that Larian's unweighted rng implementation was broken. You were statistically more likely to roll a value close to the one you rolled previously, and Larian introduced the "weighted dice" to fix it, essentially by making it much more likely that the next roll would be the opposite of the previous (high if the previous roll was low and vice-versa).
Not sure what Larian has done in the intervening 5 patches, if anything, but I don't think anything has been mentioned in the patch notes. Though I have a vague recollection that Weighted Dice was maybe changed to only work in the player's favor, changing low rolls to high...?