Best: Smuggler for me so far. I'll be playing IA for its story soon though. But I'm really attached to Mako on my BH. <3
Worst: Jedi Consular. Really boring story from beginning to the end of Act I. Didn't bother doing anything past that.
If you didn't bother to actually run through the ENTIRE story you can't say with any certainty that it was the worsed. It starts off slow but it picks up towards the end of act 2, and the ending is epic.
IMO the worst is the Trooper story line. There is absolutely no story, and I hated Garza what an annoying Beep.
But Dorne's story is what kept me going lol.