Roqua, are you looking for AI to duplicate human intelligence ? It's never going to happen. Hell, even the holodeck in Star trek had bugs.
Although I'm playing WoW right now I have limited experience in MMOs; I've actually found very little RP in my PVE WoW server: people trade, beg for money, group to kill tough monsters. . . The possibilities are simply limited, just like in SP. Are RP servers different ? The problem in MMOs I think is that everyone is playing the same role, everyone is trying to kill Van Cleef and no one, if he so desired, can instead side with him.
And you're right that's it up to the devs to make a game really stand out when it comes to roleplaying, and sometimes they do succeed. That's why my all time favourite CRPG is Darklands. It's true that it could be repetitive -- like all sandbox games, I suppose -- but the possibilities for RP were many: you come upon an isolated house in the forest, and are offered some choices: peek through the window, bash open the door, leave, etc. You see that a young woman lives there. What's a young woman doing alone in an isolated house in the middle of the Black forest in 1410 AD ? Well she's doubtless a witch; when you go to her you're offered another series of choices, such as killing her, converting her to Christ, bribing her for potions, etc. The thing is, she might not have been a witch after all and you may have murdered an innocent, or she was a witch and you've left a satanist off the hook. And that's just an example. I remember once having my party being arrested inside a city wherein my reputation was disastrous. We resisted arrest, were thrown in jail, escaped, were captured again and brought to the stake. . . In the end only one from the party escaped with his life, and the sequence -- as best as I can recall it -- was so unbelievable that I didnt reload an older saved game but continued playing with my remaining PC (you could create other characters anytime and form a new party). How many MMORPGs offer that ? Few, just like there are too few real CRPGs.