My advice would be get out of the normal contacts and start doing zone content. The Hollows, Faultline, Striga Isle, Croatoa, etc. These provide an alternate leveling path and some more in depth storylines. Plus, they tend to be a little more difficult as well. Tip missions start dropping around level 20 or so and these missions are all fun and provide some different challenges. Then there are things like the FBSA Agent missions.
The older mission arcs from regular contacts are probably better run with Flashbacks later.