Hi NC
I too have noticed the issue with static files and before after filters.
One area where this is a problem for me is Service Workers being served out of the static file directory.
If you set a cache time of say:
staticFiles.expireTime(666);
You cannot override this using an after filter, as that code is never called.
I found reverting to 2.3 had problems with gzip encoding, due to issues with incorrect content encoding headers being sent. This only revealed itself when placing the app behind an NGINX reverse proxy.