Well, I can't speak for JoyAdmin but in my opinion it's not worth the work.
Each brawl lasts less then a week and I guess there will be some new cards / herospells everytime. Far to much work for such a small time period.
And additional it's at best a 50% win chance, because all play with the same decks. So why u would do that?
Farm with own decks is much more effective (until you won't get a reward for let's say win 100 brawls or something like that :) )
