Is it safe to rename, delete or disable system/bin/mediaserver?
This is mostly speculation, but mediaserver is probably what is used to play all and any sound on android. Some app was probably using mediaserver inappropriately, causing it to show as using excessive battery.

logcat2 is probably the process used for logging output, and is where many debug and error messages are sent to.

Outright deleting them probably wasn't smart. Do you have a custom recovery installed? What phone is this? Your best bet is probably to restore those files. If you don't have them anymore, get them from an identical device.