Taris felt like it had a story that went all the way through, including a conclusion. When I thought I was done with the planet, and went to leave, I saw that the guy who greets you wants to speak to you again, this leads to some more missions, as well as a conclusion to the planet story.
If so, then I'll have to go back to Taris to check this out.
Anyhow, Taris [Republic] did not have a LINE of quest that continued one right after another like Balmora [Empire]
Balmora [Empire] you are greeted as soon as you enter the planet by an Imperial who tells you about how Balmora is an Empire planet but recently has seen a Rebellion and blah blah blah. This quest [like your class quest] sends you all throughout the planet as once you complete one mission, you are directed to go to another part of the planet to speak to someone to do another mission. Once that mission is complete you are sent to another part of the planet to do another mission. Once that is complete, you are sent to another part of the planet to do another mission. And this continues until you are at the "end" of the planet and you have a boss that completes this chain of quest.
This is different from the other world "side quest" which begins in one area of the planet and ends in that same area, not sending you all throughout the planet.
So essentially Balmora [Empire] was setup like this:
Class Quest - This is a series of quest, all connected to each other that specifically pertains to your class story and sends you all throughout the planet.
World Story Quest - This is a series of quest, all connected to each other that specifically pertains to the story of that planet and sends you all throughout the planet.
World Side Quest - These are individual scattered quest, none connected to another that sort of relates to what is happening in the World Story Quest but on a much smaller scale. These do not send you all throughout the planet and they usually start in one area of the planet and end in that same area.
Heroics - Much like World Side Quest but on a larger scale with higher difficulty, often needing groups of 2 or 4 to complete. Like the World Side Quest, they start in one area and end in that same area, not sending you all throughout the planet.
For Taris [Republic] it seemed like there were only Class Quest, World Side Quest, and Heroics.
But if what you say is correct, I will go back to Taris [Republic] to see if I missed anything. I did EVERY quest possible on that planet and when I was leaving towards my hanger, I didn't see anyone wanting to talk to me or anyone displaying an empty or full triangle above their heads. Maybe you were thinking about Taris [Empire] which I have not played yet, but again, I will go back and check it out.