Here's a video I made of boosting ST. After doing it many more times since making it there are things I changed but it will give you a good idea how to boost there.

There's a couple more pulls you can do here so you don't hit the instance limit. Just remember some of the other areas in ST will reset if you move too fast.

35-45 boosting in Sunken Temple

Skip the boss that I kill in the video if you just want xp.