I've tried tons of decks presented here. I'm admitting that the decks I tested weren't full power, as I had about one third of the cards upped. Result of winning in silver league (not counting rare EM's) are about 26 electrum, lower than EM'ing AI3. The games are much slower though due to unpredictability of decks you're going to face. I'm not sure, but I get the feeling arena matches win more cards from spins compared to AI3.
I tried one deck that could completely shutdown opponents decks. It was really slow to play, but I did manage to get EM on gold league (~350 electrum) twice. The problem was that the deck lost way too many games. Losing in arena costs both time and 15 electrum coins. Losing against AI3 costs 10 electrum and is very rare with TADAbow, which I have completely upgraded.
The swing is huge. According to this study (
http://elementscommunity.org/forum/index.php?topic=21923.0) TADAbow wins about 33 electrum per minute. If we assume around 80% win rate for silver league, +50% time for games and 20% of wins as EM, formula is (win 0.8*0.8*26=16.6 , EM win 0.8*0.2*104=16.6 , loss 0.2*(-15)=-3 , (16.6+16-6-3) / 1.5 = 20). Notice that even if matches took same time as farming AI3, it would still be only 30.2 electrum/minute with these stats.
Am I doing something wrong? Is Arena viable to electrum farming?