Hi. Fellow gamedev and 25y+ D&D player here.
While I love the option to have Karmic Dice in the game, it feels wrong to have it On by default. Since BG3 sells itself as a D&D game, using D&D mechanics, it's "wrong" to change the base/core experience of a table top RPG (the dice roll) by default.
Many (most?) players won't even know that option exist and it's bound to piss off table top RPG players when they are late in the game and find out about this option (happened to all my friends who are experienced table top players, they got seriously pissed to be playing like that without knowing).
My suggestion would be to have a popup explaining the feature and asking if you want to turn it on or off when one starts a new game for the 1st time. That way players will know the option exist and can decide for themselves if they want to use it.
I'd personally go ahead and set it to default off on top of the popup, but that's just my personal opinion. You can keep it on, as long as we have a popup to inform players of this core mechanic change.
Thanks!