Hi Mihai,
when migrating to v11.4+ the existing http-classes will be translated to the new policy rule syntax.
Unfortunately there is no feature parity and you may miss the RegEx support.
Policy rules just allow "starts_with", "ends_with" and "contains".
That´s why I used to rewrite to logic to iRules (manually, as I´m not aware of a tool).
Assuming your http-classes follow a single schema we can try to provide a sample iRule reflecting the http-class logic. Would you please post a sample http-class (exerpt from /config/bigip.conf)?
Thanks, Stephan