First off the game being completable while killing everyone is something larian is proud of and try to ensure. (Their N+2 approach) I am in favor of it staying.
That being said getting better rewards, be it loot or access to other side quests and anything else for talking your way through something can be a good gaming experience as well.
D:OS 1 had certain fights that could be avoided with a speech check, so the groundwork is already there.
The consequences of trying to murder your way through the world in D:OS was people being hostile that would not otherwise have been and loosing out on side quests.
As for the idea that lower level enemies (bandits) would not want to fight with some big hero, you can generally view that as one of three things from a story perspective ignorance, over confidence or fear of someone bigger forcing them to fight.
An interesting mechanic that might prove to not be worth it from a fun gameplay perspective is giving enemies the option to surrender or flee if they feal a fight is hopeless (just blew up all theirs friends with a meteor shower for example) ultimately though I think it would be frustrating to lose out on XP/ loot from enemies who fled.
All that being said the greatest hope we had for more charisma based encounters was the bard tree option that lost out to polymorph and summoning master.
