Maybe they changed it from EA, but by and large the Karmic Dice made higher rolls more probable, so you don't miss dialogue checks so often and have more hits in combat. Which, other than most posters in this thread assume, usually benefits the player more than the AI. Because the player can deal with the higher damage/less misses environment much better than the AI, from my experience. That's the reason why Karmic Dice is the default option and you have to disable it. I'm playing without Karmic Dice to make it a bit more fair for the AI, and to make defense (AC) more important.
