I'm not saying the game isn't enjoyable as it is, or that the story for this era isn't allowed to be better than the original trilogy. I'm just saying that for the casual gamer and casual Star Wars fan, the more closely it sticks to the original trilogy, the better.
And I'm not saying that there aren't any cool Star Wars elements. I think the Jedi & Sith powers are very well done. And my BH feels very much like I would expect a BH to be.
And there definitely are some good "trilogy" companions, like Jawas and Wookies. I think it would have been better to get them before other non-trilogy companions.
For example, I've lost count of the number of bugs & monsters I've slain. Whether it's rakghouls on Taris or Killiks on Alderaan, i've killed a lot of bugs. But I think I've only fought a handful of rancors, and no AT-ATs or AT-STs.
First 2 post should've answered your question. No at-at or at-st because they don't exist yet per game time line.
And this era is fine for an mmo..Mr. Lucas has a tight reign on what you can and can not do in the timeline he created. Ergo why they did it in the past, as long as it doesn't meddle with what is in the movies or what Lucas has in his "bible" then they are free to do want they can, with permission of course.
As an example, I'm pretty sure that Mr. Lucas said no to any type of jedi wookies , that was after Lowbacca btw.