Another good chapter, lots of developments. Minerva should really have caught on to Dumbledore this time, unless she's already had some of his 'loyalty potion' at an earlier point. I'm sure Snape sees through him but he's too Slytherin to make a direct confrontation when it wouldn't gain him anything.
Albus is a Master Alchemist; he wouldn't have tried a mass-dispersement unless he had tested the formula in a pilot group. You can even see the lingering effect in Hermione's response to Holly.