because it is also a minor nuke/several DoTs and a couple of status ailments all rolled into one handy package.
"Deals DMG, to a single enemy, with Mordred's current element and applies ATK↓, DEF↓, Poisoned, Scorched, Putrefied, Drowned, Blinded and Dizzy."
and it stacks with D'arts debuff.
Mordread also has "Vicissitudes of Fortune" Affliction RST↑ to all allies and Affliction RST↓ to all enemies, so landing the debuffs is easier.
as well as "Black Propaganda" Increases enemy's max Overdrive Meter↑ by one.