In contrast to many other RPG titles, the new installment of Torment enables the player to complete majority of the game without fighting. Simply skillfully navigate your way through dialogues, avoiding provocations or willingness for direct confrontations. Every quest has many optional solutions and using violence can be avoided.
It is worth mentioning that usually the game offers experience points for completing quests - it doesn't matter how you do it. The difference lies usually in what items, cyphers, shines and tidal bonuses you receive. You can focus on diplomacy and use effort points in conversations for convincing your talkers to do what you want - battles aren't awarded with additional experience.
If you decide to play like that, you must improve the following skills:
Each level of these skills will increase success chance for using these skills in dialogues by 15%. You should develop them so that you can successfully use them to solve quests in diplomatic way.
By default you should also choose Jack class and give the character the Charming descriptor (Persuasion +1, Deception +1, Willpower -15%, Intellect -1), so that you can complete quests easier.