Been thinking about that as well, but there's only one real way of "farming" gold... and that is to just wait, patiently, for dailies to reset. And nobody got time for that shit.
Arena is completely out of question. Back in the GOOD'OL'DAYS, I actually got ~120 gold + deck per arena run. But two days ago, just after reset, I gave arena like 10 tries and the best run I had was 4-3. Needless to say, my head didn't feel very well after headbutting the wall on my right after the shitfest that was arena that day.
edit: are you supposed to have 1 or 2 abusive sergeants?
edit 2: waiting and grinding gold for Naxx will benefit me how, exactly btw? I mean, I'll still have the same shitty cards and whatnot.