Assuming you could clear it at a decent rate... would you actually farm Arena? Even if I could farm Arena (never stepped inside arena so i cant farm it) I wouldn't because I dont have a lot of spare sta after doing all the events Gungho throws at us. Not to mention I have 70+ piis of various colors sitting in my box doing nothing. Arena to me just doesnt seem like a farmable dungeon because of the stamina cost....unless you are a heavy IAPer. Which then brings the question of why do people care about making optimal Arena teams if they aren't farming Arena?