Which version of TMOS are you currently running on your F5-LC units???? if you are using version 10.x.x or later you may get alot in terms of report if you are still using the version earlier than this you will not have a very comprehensie reporting. Also what you will get in terms of reporting is the total utilization of the link. As your users dont directly go out so you will not get the reporting on per IP bases which you may be expecting out of it. If you still have a F5 support for this box I will prefer you drop them an e-mail and they will let you know what reporting you may receive out of all.
Regards,
Nimbostratus