Librarians have enough raw power than they can still kick ass while Fettering their powers, so you only need to Push against boss enemies. There aren't any tricky talents though - the talents that help you channel better or reduce phenomena/Perils chance are pretty obvious.

The one DW game I played a while back, the Librarian got proficiency in heavy Melta weapon and carted a Multi-melta around, firing it and launching Smite blasts alternately as the melta cooled off. Between him and our Heavy Bolter Devastator, we pretty much annihilated everything.