Everyone in this thread is wrong. Being champion no longer determines the entrance order. Being a heel doesn't bring you out first. For example, there are many times when John Cena comes out to the ring first on Raw, right after coming back from a break. Then you have the heel coming out first so you can have a face pop.
The entrance order now depends entirely on how the WWE wants to manipulate crowd reaction. They try to balance optimize the entire show to keep fans from getting cheering fatigue. Don't try to figure out any pattern, there isn't one beyond what I just said.
That doesn't make sense. I agree with the crowd manipulation, in a much broader scheme than that, but the cheering fatigue doesn't make sense. Mostly because an average entrance is around fifteen to twenty seconds. I don't understand how that time frame makes a difference to regaining energy and avoiding fatigue, especially if the heel is getting a large reaction as well. I follow and fully believe that theory when it comes to booking and match placement, such as why there is usually a divas match or a lesser gimmick match in between the world title matches, but thats about it. And yes, hypothetically there are alot of children in the audience and its fair to assume they may get tired, but most of them are just so excited to be there they stay pumped until the end, and then crash. It's not like the main event often gets a dead reaction. Unless its an experimental ME, its usually the top reaction, especially PPVs, where there are less segments between matches and more matches overall.
I am completely with anyone who said the champion should traditionally come out last. It's a perk earned by being given a championship, and when its reversed, unless there is a reason, such as an attack or a surprise opponent, I do find it disrespectful. Well, I don't really care anymore, but I find the idea disrespectful. American wrestling has lost so much luster that its lost its own integrity. There really are a thousand factors, I suppose. The face coming out last seems to be a major one. Crowd manipulation as well, such as Vince trying to force or test (mostly force) a reaction upon a certain wrestler, as in the case of the Jackson/Barrett match among others. I'm sure the other reasons vary anywhere from gimmicks within a wrestlers entrance, to psyching up a dead crowd or a wrestler cutting a pre-match promo. I would even bet money it has happened several times because a wrestler needed to finish using the bathroom or finish taping their wrists or other stupid reasons.
Regardless, its a tradition that should be resurrected. It's fine for a Raw or Smackdown, especially a middle of the card random match, but for any PPV, especially WrestleMania, its completely disrespectful. Sure Cena is a god compared to Miz, but the company gave Miz the belt going in to the event, so he earned the right, by their own standards, to come out after Cena. Especially since it would serve to give Miz even more heat in doing so. The mega stars don't need that extra boost, just like the old saying that Wrestler X doesnt need the world title to be a star. It isn't going to boost your ratings by even one person having the bigger star coming out second. If you want the massive reaction to close the show, give the star the win, but either way your champions deserve the respect of being announced after the challenger, especially if they could use the credit for their career.