I wouldn't rely on any telepathic attacks from a Khornate-driven Daemonship as being a game-changer, really. They'll be unpleasant, and a weapon to consider, but Khornates are the weakest of the four primary factions in terms of offensive psychic ability - they tend far more strongly towards 'buffing' and anti-psychic defenses. Their attacks are also much more likely to take the form of inciting bloodlust and aggressiveness (not that this should be underestimated) than mind control, catatonia, or outright insanity the way daemons of another faction might.