I agree with you that experience should be related to the difficulty to obtain a result, whereas a reward system may not be equivalent.
I'll use the Vitoria quest as an example of how I see a good balance could be achieved.
Solution A: Kill Victoria.
- XP for the fight A
- XP for completing the quest as the quest giver requested
- Material reward for completing the quest as the quest giver requested
Solution B: Kill Englandaer.
- XP for fight B
- XP for completing the quest as to Victoria's satisfaction.
- material reward from Victoria
Solution C: trick Englandaer.
- XP for completing the quest as the quest giver requested
- XP for completing the quest as to Victoria's satisfaction
- Material reward for completing the quest as the quest giver requested
- Material reward from Victoria.
Solution D: Arrest Englandaer.
- XP for completing the quest as to Victoria's satisfaction
- material reward from Victoria
- small XP for arresting someone dangerous
Gaining XP is not the only reward for a quest and if both the loot and the XP are balanced based on the difficulty involved in the solution the game should provide something for everyone.
Like Neonivik said, talking the bad guy down before they summon the ultimate evil doesn't get you as much experience. You can argue that changing their mind is the more beneficial result for a world, and is difficult (probably impossible in most stories, they have their motives)
But I would still like to have more situations in the game where someone is rewarded for lateral thinking, even if that means more gold or loot. (Yes I know money was easy to come by in D:OS)
