I have not read the entire thread, but we are preparing a troubleshooting guide for this in our knowledge base. TL;DR: Deactivate all hosts, restart site and re-enable hosts, until you find one causing the usage.
I do not want to blame a vendor here, but we saw this issue with APC devices. Maybe you guys can check, if you have any of those and if disabling them and restarting the site solves the issue.
Do let me know if this helps. Thanks!