Mage dies if Monk isn't taken unawares. Which, in this scenario, Monk isn't.
It's like the old FFXI joke: A black mage walks into a bar. The black mage was defeated by the bar.
Haha lol. The Black Mage in FFXI must be pretty weak. I've noticed this in FFV, Black Mage in that game is that not really that strong at all except in its main ability Black magic but I'm only using it to master the job for endgame.