To farm hunter you need another controller.
Add me if anyone is interested!
You sure you don't wanna play DLC Co-op Arena with me? It's fun!
Also, I'm lonely.
farming arena on chateau will not get you any rare treasures, you might get extremely lucky, but take it from someone who has farmed chateau multiple times (about an hour or 2 a game) and didn't get any new treasures (seriously 0 rare treasures (duplicate or not, they were all common treasures)), hunter is your best bet, it is a terrible mode (trust me I KNOW!) but keep farming hunter as much as you can and you'll get some treasures eventually, when it becomes frustrating, play a game of arena or competitive until you calm down, then return to hunter...