What about another way to make the creation of diverse decks more common. Right now the arena decks make me yawn. The last ten arena decks I played were 8 phase-sheild decks (regardless of the oracle card???), and two darkness-denial decks (one of which had the oracle card miracle).
Neco posting dead threads is frowned upon by the mods. This one will probably be closed.
But to answer your question: Arena decks are boring because few of the decks can be successfully played by the AI. You could build an OTK deck which, when you play it can beat False Gods and Gold-Platinum Arena, but give it to the AI and it will mess it up and lose all the time
So, since most of the players are lazy, especially when it comes to Arena decks, you will see lots of copies of the same solution. Psiontal, darkness denial, immorush, etc
That is why we should upvote those decks that actually try to be original