Edit: oops, @grrarg beat me to it, didn’t catch his post at first. So just disregard this post
No actually it was explicitly stated that the classes should have no baring whatsoever in arena, cause it would dominate the arena. The exact opposite of what you are claiming was literally announced by the Devs when they previewed hero classes.
And with good reason so, cause the magic bonus absolutely does what the Devs were concerned about in the first place.
And by “new meta” in arena you mean everyone must exploit that obvious unintended behaviour of the class magic bonus or be at significant odds to win games, than this is clearly a very unhealthy “meta” for the game.
digged out the Sirrian Quote from the Hero classes preview thread