Extreme Primals are not part of the main story and that is really the place unsynced was designed for. If it is normal or hard, unless you really can't get a group (which with roulettes shouldn't be that hard) then it is a option. But, that is what it is, an option. Extreme Primals are all optional content. If you want a group that does it unsynced then gather a group together that will want to do it. It is optional content. Everything else is story content covered by the roulettes and can be done unsynced.