I did every bonus objective, heroic and bonus series I could find. I did every FP once. I have been in 5-6 pvp matches, and I spent three or four solid space mission sessions. I skipped at least half of Tatooine and all of Alderaan. I was overleveled the whole game, including on Voss. I haven't started Voss bonus quests (or Hoth bonus series either, actually) and I'm ready to START on Corellia with only 28% to level 50. I don't know how you can wind up with too few levels in TOR.