You can tell, if you look at Order of the Stick sideways, that it started out a series of jokes and evolved into a story. (Unlike No Rest for the Wicked or Girl Genius, which aimed for story from the start.) Even if he didn't admit it in so many words in the course of explaining why he's not going to convert Order of the Stick to the fourth edition. (Jeesh. D&D has a fourth edition. And the one they had been on was 3.5.)
On the other hand, it does make a plausible story beginning in media res and then developing backstory. The wonderful serendipity of things that were just mentioned turning out to be important plot elements -- happens all the time.
Still, it does make me glad for revision. 0:)
And I hope he has something sufficient -- anticlimactic for when the darkness comes off the creature.
And I note that it is not a humorous story. It is a story with a lot of humor in the telling, but the story isn't humorous -- which doesn't really differentiate it from a lot of other comic works.