Boss Drop Rate

For the sake of completeness, I observe that only Familiars and server-sided "FA skills", namely Xenon's Aegis missiles and WA's Trifling Whim arrows, de-aggro (which gets a bit annoying). All active attacking skills, (generally client-sided) FA-type skills and summons will aggro.

Hadriel

Phantom's Carte Noire is in the same category as Aegis missiles/Trifling Whim. That's how Phantom players were able to solo Cygnus when she healed 35+ times, if you could knock her back with Carte Noire it'd mean she never had aggro on your character and you could just knock her around the map for an hour until the timer ran out