I have been going at it for over two hours and I still cannot get this wretched thing!!

Ive got bandit on and could at any time just kill the little guy...

Any advice or personal expierience someone could share would be nice.

It honestly just takes forever unless you get really lucky (Anywhere from 100-1000 attempts). Isn't there another place to get Demon's Mail late in the game?

i remember always stealing succesfully when i got too tired of trying and then started to attack it while still stealing with zidane. then i get it like 1 or 2 turns before it dies. then i go yay!