If you file an ASR then you force an investigation into the matter.
Personally, if I felt that concerned, I'd cut and paste your comments in an email to the CP or Base Captain.
Not sure if you have flydress at your company, but if it flags up that you are unstable on approach and you've done nothing as an FO to bring this to attention, it'll be your @rse on the line as well as the Skipper's.
Forget the fact that this guy is experienced and close to retirement. If he is genuinely affecting safety and going outside of SOP's, it should be brought to the relevant people's attention.