Do you have a lot of photo, video, or music files in Internal Storage? If one of those files is corrupt, it might cause the system's Media Scanner to get hung up on that file, which increases CPU usage and drains battery. I'm not sure if Media Scanner is part of Mediaserver, but if you do have a number of media files on Internal Storage, you might want to try moving them off the phone, perhaps by connecting the phone to your computer via USB and copying the files over to the hard drive. Then delete the files on the phone.
Edit: According to this article, Media Server and Media Scanner are the same thing. See if the tips there are helpful:
http://geeknizer.com/fix-android-med...battery-drain/