"I think that there is a strong case to be made for more objective-based XP (such as XP for clearing a wilderness area of dangerous beasts, XP for the handling of the scripted events, XP for exploring a ruin, etc.), but I don't see any merit in the arguments put forth here for per-kill XP." (Grimreaper659)
I agree with the first portion of what you said--there is a strong case for a more advanced experience system; the second part I still believe there are merits to a per-kill xp system.
Now if the more objective-based xp system gave you rewards for a certain amount but perhaps not the full amount of a certain trash mob type in a area it would make sense if the completion reward was not a lets go fedex so some mob somewhere can slap my back with xp but instead something akin to a global effect ...(e.g., your party renown has increased, party member b says 'that was a hard fight i think we learned something' and you get xp, ...you feel yourself more advanced at killing this mob type and better at salvaging the parts).
Without these global rewards but instead the gamer having to hunt some random mob to thank the party with a exp backslap the games pace is off. You end up with scenarios which I experienced where I just went exploring and killed things that seemed logical for my characters role to want to have done but then find after a hour of play i achieved nothing until i went and talked to every npc in town to find the ones that would xp backslap me.