I have done more knight bosses than even smuggler bosses with either my smuggler or my shadow. I was paranoid about playing as a knight, but so far I haven't had to call anyone for help. Think it is largely new players are drawn to Knights and most of the time I have noticed they are not correctly equipped.
@Tommycat - I know that quest well. It is still the only leveling quest in game where I have had to call in help to get past it. Still annoys me, want to reroll another sawbones just to prove to myself I can do it solo. Brem had to call Lynk and Mav to get past it after spending every credit to her name on medpacs and repairs. I think I died 30 times and almost quit the game.
Shadow and Agent haven't had any problems soloing everything 2 man and below. Weird playing and not dying out of every cutscene like I did with my smuggler, especially with my agent which is basically the same class. I guess the difference is now knowing a little about MMOs and knowing equipment. Even beyond that knowledge, solo leveling DPS is so much easier than solo leveling a healer.