Something is wrong with this.
I had the JB update, and since then Exchange is consuming my battery.
I don't think that this is a calendar sync issue, because I'm only syncing my mail.
Now I'm trying to delete my account, and I will see.
I also notice that sometimes the battery is heat, even when I'm not using it.
By the way: what kind of e-mail are you using? I'm using hotmail. Could be a problem with hotmail servers, rather than problem with my mobile? Maybe it can't connect with server and has to try again, and again, and again.