It's funnier if they're just completely retarded. 
I humbly disagree ^^ I think the ludicrously retardness is a bit... silly. I think you could do something a lot more clever with the NPCs. I agree they shouldn't make much sense, but just differently to what you have at the moment.
Just as an example you could have harnquist as a psycho killer mentality dude, maybe a very polite psycho killer mentality dude.
Eliseth: Hello Harnquist, I need help with these ores... could you...
Harny: Yes I agree! Daggers are most sharp indeed, and quite cute too, don't you think?
Eliseth: ... erm..
Harny: ... 't pierces flesh. Can I help you dear lady?
Eliseth: Well see I...
Harny: HAHA! funny girl. *stabs himself in the arm*
Eliseth: Mother of Laanx!
Harny: Mmm... hehehe... such a pretty red colour. Have you noticed that when you see blood you start feeling dizzy?
Eliseth stands still... shocked.
Harny: Can... I... h.. help.... ... you *drop to the floor*
Suddenly a noob walk past.
n00b1: Oh cool! Free weapon! *pulls the dagger out of harny's arm and walks off happily*
Eliseth stands still... in shock still.
Well anyway, thats my view, being completely retarded will
maybe be funny for the first two cartoons, but it will get boring eventually. Otherwise this whole cartoon is a potentially excellent idea.
Regards
Eliseth