journalctl is a critical component of any systemD based distro, it turns out it isn't enabled or running in 7.0, this is a problem as many very important logs utilise journalctl.
For example we realised that after upgrading and setting up snmp the daemon wouldn't start - so I turned straight to journalctl to see what errors had occurred this current boot but it wasn't available.
The solution is simple, simply enable the journalctl service with systemctl, then start it.
service systemd-journald start
Redirecting to /bin/systemctl start systemd-journald.service
You'll also want to make sure that logrotate is indeed correctly rotating logs, but it should be an easy fix otherwise.