Hardware and performance

My first guess is a problem with your Moodle hoster. If you can access other service in the Internet at normal speeds why not Moodle?

I would not manupulate inhouse cabling. Moodle does not require any special networking! The only place to check is the DSL-modem/router, especially deactivate firewalls during testing.

I hope your Moodle hoster knows about Moodle. It is not just any website, it is fully interactive and requires lot of ressources. Cheap hoster often get "surprised" by the needs of Moodle. I also hope your hoster has technically competent staff to monitor the server and give you access to those performance graphs. "We have bigger customers" is just big talk.