Millbrook is by no means a bad football team. Regardless of the difficulty of their schedule, "okay" teams don't average nearly 44 points per game. If anyone underestimates them in the playoffs, they would very likely end up looking silly like LCA did last year when they got blown out of the bracket 65-18.
I think their schedule will hurt them this year though. The one good team they've played leveled them, and they're very one dimensional. Don't get me wrong, losing to Woodgrove is nothing to be ashamed about, but there are several other teams out there which are comparable to them, so unless Millbrook has improved drastically since that game I can't see them getting past any of the upper seeds. They shouldn't have any problems winning their first home game, but they would have benefitted by playing an Eastern View or a Louisa-level team in addition to Woodgrove.
I think a big teller for them will be the Sherando game two weeks from now. Sherando doesn't have a particularly good run defense, and their offense hasn't been spectacular this year, so if they aren't able to put up big numbers against Sherando I can't see them staying within a couple touchdowns against the likes of Woodgrove, Salem, Amherst, and Byrd.