The first thing that comes to mind is, "this parody doesn't even work on a surface level -- that's not how the script goes!" Panel 1 has got the revision correct, then panel 2 flies off the rails. "Why did he let her think he was dead?" Well, all he did was go through 3+ separate trials and chase her down himself, but I guess he could have kept in touch. Panel 3 implicates Westley even though he doesn't admit to murdering while being a Dread Pirate in the movie, and he wouldn't have to anyway if each Dread Pirate passes the mantle on to the next worthy captive. The Dread Pirate's ruthlessness could very well be a mass delusion, which I always took to be the joke of the Dread Pirate's very existence. But these are nerdy concerns.
I count three punchlines in the last panel: "Westley acknowledges the narrative," "Buttercup rejects the narrative/pursues Inigo," and "Westley uses 'As you wish' to desperate/bitter effect." As much as Randall's geek-movie piggybacking annoys me, I think taking characters in new directions has potential, but not like this, where we're left with a Hollywood romance flipped into a breakup. And if Buttercup were so against murder, would she necessarily prefer Inigo, a sword-for-hire? Westley (hypothetically) killed to survive on his way to Buttercup; Inigo does it for cash.
There's a better joke hiding in the alt-text, with the idea that slash writers would've rewritten the movie to fit their tastes, but the execution's just a bumper sticker in the alt-text. If only we could address Randall in person...
Randall: Why do you do this?
Carl: Because you had a beloved comic in your hands, and you gave it up.
Randall: But my fans would have forgotten me if I waited for good ideas!
Carl: Your comic lives and you rely on movies -- (to the fans) -- True comedy saved him in the early days, and he treated it like garbage. And that's what he is, the King of Refuse! So, bow down to him if you want. Bow to him. Bow to the King of Slime, the King of Filth, the King of Putrescence. Boo! Boo! Rubbish! Filth! Slime! Muck! Boo! Boo!
[tl;dr version = Comic didn't get the parody right, wasn't funny in any of its punchlines, booo]
thomas: i changed a few tiny things about this post - added a link to the comic and a comic # to the title --carl