To add to this, there are times when you will be given two class quests on two planets and you need to look at the level of each quest to see which one you are supposed to do first.
I made that mistake too with my first character. I went to Nar Shaddaa and got my butt handed to me (especially by a particular Bonus Mission boss in Exchange territory). Only then did I see that Balmorra came first.
They should separate those better, I think.