In which I overanalyze Harry Potter and the Deathly Hallows: Part II

Um, spoiler alert, people. (Actually if you don't know how Harry Potter ends, just go away now.  I don't think I want you here.  I have standards.)

Oh, also:  nerd alert.  You've been warned.

So, I keep reading that people had a problem with the way Voldemort just believed Narcissa Malfoy when she told him Harry was dead, and never checked for himself.  This bothers people, because really, you've failed to kill this kid how many times, wouldn't you make sure?  I guess.  I can believe, though, that Voldemort's general, all-around hubris would lead him to believe that none of his henchpersons would dare lie to him, especially a Malfoy since they're so pathetic; really what reason would he have to suspect a sniveling terror-stricken Malfoy of having the guts to lie to his face about such a thing?  So I'll buy that one.

My problem (you knew I had one, right?) is with an earlier death: Snape.  Voldemort believes Snape is the true owner of the Elder Wand.  And says as long as Snape lives, the wand won't be his.  But doesn't he mean that he must be the one to kill Snape, to effectively disarm him and thus claim his wand?  I mean, if Snape fell off a cliff, it's not like his wand would just jump into the service of whoever picked it up, would it?  Don't you have to win the wand?

That certainly seems to be Harry's assertion later, when he explains that the wand belongs to him because he disarmed Draco.  Not even killed: disarmed, and not even while Draco was using the Elder Wand!  So apparently all it takes is a well-placed expelliarmus charm to transfer full ownership of a wand from one wizard to another; clearly it's the disarming, not the death, that matters.  [Totally not the point but wouldn't there just be like, random and chaotic wand-loyalty-transference happening all over the place? These kids have been practicing disarming spells since Year 1!].

Granted, Voldemort didn't know all this, about the disarming being enough.  He's focused on the death.  But still, I would think he would grasp the concept that whatever is done to capture the wand from another wizard, if he wants the wand to be his, he should probably do it personally.  Right?  I mean, just to be extra safe?  Right?

So why not just toss a quick and dirty Avada Kedavra Snape's way and have done with it?  Pretty much every other murder he doles out throughout the entire series is committed this way, isn't it?  Voldemort is the king of Avada Kedavra.  It's like his number one hobby.  So why is this death, which is so deliberate and important at this point in the story, different?   

Voldemort doesn't kill Snape at all.  He slits his throat, all sloppy, and then sics the snake on him and saunters away oozing nonchalance:  Eh, he'll die soon enough, I'm sure, and then the wand will most likely be mine, and then, you know, if it all works out, I can continue to carry out the plan I've been obsessing over for 17 years. I mean even in the best-case scenario at this point, Voldy, you didn't kill Snape!  The snake did!  And if that wasn't convenient enough for our heroes, Nagini had a big lunch and wasn't even hungry, because he, too, slithered off with his job half done, opening the door for Harry to slip in, watch Snape die slowly and dramatically, and gather his shiny memory tears which hold the key to the entire series.

No.  I'm sorry, Jo.  I love you tremendously.  But...no.