Correct me if I completely misunderstood your statement here, but are you suggesting that what origin characters do while under the control of the player should be considered canon or something to that effect? I'm just saying because I think that opens a big can of worms. Can't Karlach also raid the grove and massacre the Tieflings too? (while you play them as an origin character).

While yeah, that's possible, in an alternate universe where Karlach is comically evil, it kind of goes against her entire actual character. Origin characters don't have alignments, but I think there are certain things they were specifically written not to do or agree with. When you boil it down to that level, there's no argument to be made because nothing is static.

You can never have enough choices, I agree, but they still need to be well-written choices so that they can make sense. Maybe it would make sense for Karlach to massacre the Tieflings, if there was proper build-up towards that end. I'm not a professional writer, but I imagine consistency is pretty important to crafting a good story