Although everyone is hyped about the new minion book, I don't think minions should be the Arena prize. I was really starting to enjoy resuming playing WoW (as the Arena was the only way I could get new warriors). I wouldn't mind if they were in the Green Door or Tower prize. I think if the green door consisted of 2 special, 2 minions, 2 legendaries and 2 super rares that it would be fair.
Also I think it's about time that the achievements area be updated. This would allow the game to be more interactive and players would actually have something to look forward to instead of just completing the books. It doesn't have to be difficult challenges and the prizes could be items like gold ingot etc. It would be nice if we can get an abundance of these items and not just rely on the Daily Reward.