I don't want to ruin the game for anyone, but sharing a winning strategy should benefit everyone, because everyone can adopt it and then everyone wins, right?
The basic principle behind my strategy is simple: Elements requires grinding; he who grinds the most wins! You can grind more than you are currently grinding to achieve this; better still: get everyone else to grind less.
We all know that the lvl3 decks are boring to grind, yield very little electrum, and rarely yield useful cards on the spinner. Most clever grinders will grind away in the arena. With this in mind, the strategy is to make the arena as boring and unpleasant as possible in order to ward off other players, who may otherwise enjoy the game and grind enough to catch up to you. Long term, the strategy is immaculate, as the logical end game is that everyone except one person gets fed up an stops playing: whoever has the most patience wins by default!
So, how do we do this:
1) Put earthquakes in your deck. Lots of them. Even if they have nothing to do with your theme, put them in there because if the AI wielding your deck gets one or two of those nasty suckers out on turn one you will cripple the human players game. The pathetic human will usually just quit and cut his losses!
2) Look up good decks online and simply copy them. There are a finite number of cards; probability is a complete science: there are a finite number of good strategies and one which is statistically better. Interestingly, this point isn't effective because it makes your deck strong, it is effective because it bores your human opponents to tears. The pathetic human will usually just quit and cut his losses!
3) IGNORE THE ORACLE CARD! Seriously, oracle cards can introduce a very dangerous element of creativity (element:entropy) into your strategy. An attempt to incorporate an oracle card can prevent your from using a tested and true cookie-cutter strategy (above); quizzically, however, the presence of a seemingly irrelevant oracle card which has nothing to do with your cookie-cutter deck can add to on opponents frustration. A frustrated human opponent is a defeated human opponent. The pathetic human will usually just quit and cut his losses!
4) Throw as many weird cards as possible into your deck, as in the trusty speed-bow deck. If your opponent manages to stave off bored-madness long enough to defeat you, the inclusion of more than twenty different cards will guarantee that no matches come up on the spinner; you may not have crushed him in the game, but you just crushed his spirits! Oh pathetic humans.
***) This is an incomplete list. Please add more ideas for the utter obliteration of any possible enjoyment which a human player may derive from the arena. If we all win, then no-one loses, right?