As far as I can see the directive would require ISPs to record what sites I visit, not what I do on them. Isn’t this what they already do?
No, ISPs do not record what sites you visit. At least none that I know of (and I work in the industry). Why would they ? It would be outrageously expensive, for no gain.
Isn’t that information already available following a warrant anyway?
Well no, as ISPs do not record what sites you visit. They can put a tap on your line after a warrant though (Lawful Intercept), but that is for one user specifically, and nothing is recorded- a copy of the data that passes over the line is just sent in real-time to the justice department.