I would definitely support goal/accomplishment-based XP instead of kill XP.
Why choose. Take the total xp for combat of mobs and simply give it to the character when those mobs are pacified through means which do not involve combat. Viola.
Because, we can kill friendly NPCs and get exp for them. So with exp for talking through and killing being 2 separated things, we would be able to get twice as more and go overpowered. Need the third way, the third way is "achieved a goal = got exp, everything else = no exp".
