hi, sorry its been like a day since i checked back here but i used the same deck to farm Mai lvl 40 with Labyrinth Builder. this is the luckiest ive ever been getting two prismas in one duel, its crazy. :)
Labyrinth Wall deck will also work. It's 100% win. Most of rex's cards will change stuff to defense position but because the wall is 3k defense and prefers to be in defense position, rex can't stop it.
Proceed to prioritize draw and use vassal union or piranha direct attacks for ez 8k.
Have fun! But of course it's level 30 rex, level 30s drop nothing and it statistically have been proven to drop nothing.
You haven't played long have you? Yes the drops are there but they are near non-existent. You just got lucky with the drop. I've been farming all level 30 roaming duelists and they all have just been a complete waste of my time. They drop nothing good, a good 5 minute waster at best. Out of 50 games, ok maybe a level 30 will drop 1 , JUST ONE SR card but that's it. I rather have my 2 hours back.