With my Jedi Guardian, there were only two bosses I had trouble with on Tython. One was an elite somewhere at the end (which, actually, is an optional/bonus fight) and one of the Flesh Raiders. Don't know if it was the one you're talking about, but it doesn't matter. As Lynk said, it's best to complete quests from one town, then move on to the next. Also, do the bonus quests, they yield a good amount of exp. Especially do the bonus quests which work in stages, as they yield exp after every stage completed and an extra big amount of exp when you turn it in. If you do all that, you should always be at a higher level than your story quests.
Make sure you regurarly replace your gear with better gear, as well. It can make the difference between success and failure. It must be said, though, this depends on the specific classes. My Bounty Hunter blazed through Hutta, its starter planet, without much difficulty and without having to upgrade his gear every level. On the other side, I found it best to gear up my Jedi Guardian as best as I could even on Tython.
Last edited by Miltiades; 03-18-2012 at 02:19 PM.