I'm for non-violent solutions but if you are going to have them please make those solutions meaningful and in keeping with character motivations and goals. Pay attention to world coherency - a non-violent or violent solution shouldn't undermine that. *Stick to the rules laid down by the fiction of your world* Divinity is floaty enough as it is with its lore.
Here's an example: If you could manipulate an army to stop sacking a town then great but it requires very good writing. Done poorly and at a certain point it impacts the plot, a believable world and its inhabitants. Why would an army bent on conquest just stop unless there is a compelling *material reason* for them to stop. The "You and whose army" retort comes to mind here.
Also it shouldn't always be possible to find a non-violent solution aka Doctor Who in his first meeting with the Daleks. The Daleks plan to wipe out the Thals and they can't be reasoned with. The Doctor must persuade the Thals to attack the Daleks or they will be destroyed. No ifs or buts or maybes - that is the only option. If the Daleks could of been reasoned with it would of destroyed the menace of the Daleks and what they are about.
I don't necessarily think it should be necessarily 100% no-kill. RPG plots generally need a scary bad guy, and often they can only be defeated via some form of murder.
However, I have been impressed by how this was handled by the game Metal Gear Solid and similar stealth games. Successfully infiltrating an enemy base without being seen and without killing anyone is a great achievement that the games actively reward you for. This is an example of a game for which violence and killing is only a secondary mechanic.
Metal Gear Solid also provides one of many possible solutions to your problem. In MGS, the evil army has a secret weapon. Your mission is to destroy the secret weapon, and not to stop the war. But even Doctor Who's solution is fine. It's very different from simply fighting your way through the evil army until you meet the boss and then kill the boss. Outside of video games, heroes often have to find a more rational approach.
The problem at the moment is that D:OS doesn't really have any strong non-combat mechanics. Sure they could write some good story-driven solutions to problems. However, game mechanics for things like stealth or diplomacy simply aren't very robust.
