The Arena makes no sense anymore. As time passes, the levels and skills have decreased a lot since you have to play with weaker and weaker opponents. From a competitive point of view, the system is worse than the original ELO.
And even more, you can see players with 1800+ who simply grind ELO versus weak players.
Just imagine that you have top players who accept "under-elite" players, which means they state "I might become "arena champion" and beat only opponents ranked around the 1000th place". Ridiculous.
In my opinion the system is a complete failure because instead of putting you in great games versus tough opponents, you're randomely paired with very bad players who influence a lot the game through their bad plays. The best we can do is that all good players add themselves as friend, and open tables to play between themselves. Even in training mode, it doesn't matter in the end. I just want to play interresting games, and it has become more and more difficult.