So, if this were Pact, I would expect that Dumbledore has one of Voldemort's Horcruxes, and he can be possessed by Voldemort at will. Dumbledore would show up to save the day, and then the brief uptick in probability of success would be followed by a precipitous drop.

I am fairly confident this will not happen, but I'm noticing that most of my confidence seems to come from arguments that I am not confident in once I give them explicit form. For example, that seems too hard an antagonist for Harry, and he needs to have some chance of success, and EY seems against giving the protagonist the plot armor* that Wildbow gives them. But when I observe that this is an outside view argument that's reference class specific, HPMoR seems much closer to Worm or Pact than to other works of fiction, which says I should expect it to follow the same convention. Thoughts?

* Typically, Wildbow protagonists look like they're taking two steps back for every one step forward, but I see it more as "trading away parts of themselves / resources for success, and eventually getting to the end goal / end of the story." If you predict that they will eventually win but it will be the most Pyrrhic victory possible (over the long haul), I think you have a good shot at getting all the details right.