As the title says. I see three Fighters and three scouts. How do you unlock more, if that's even possible?

So I've been playing a sage for a while now, but it's starting to get dull, so I made an inquisitor. I dunno what route to take her, though. I want to spam lightning, but I fear that spec will wind up too much like my telekinetics sage. Does the assassin side have any good lightning spam? Can I still be a viable spellcaster if I become an assassin?

Thank you for the info everyone! I don't really mind if leveling is easy, to be honest. I just worry if dungeons and raids and the like are too easy. For example, in WoW, it has gotten to the point that you almost never need a healer or a tank in most dungeons, thanks to everyone having powerful self-heals and the ridiculous amount of good gear that is spat out everywhere. I've even seen NEWER raids beaten with less-than-max-members groups with poor party composition. I know this because I've seen (and done) it myself. Basically, I'm hoping SWTOR still takes some skill in the later level dungeons, and in raids. Or whatever the SWTOR version of a raid is called.

And shockingly enough, we went through without a single death. It was the Esseles, or however it's spelled, so a level 14 group. But it was full DPS, with one person still a knight. Hadn't even selected a specialized class. Needed everything too. Couldn't kick him either, one person never spoke, and the other insisted the guy meant no harm. Does the group finder do this often? I'm worried, I don't want this game to go easy-mode like WoW has. Some semblance of difficulty is part of the reason why I like this game.