Now that I finally got my sentenils up to level 21, I'm thinking that I can level these guys up pretty efficiently by doing only a couple of things:

1. All class quests - this game is all about the story
2. Only doing the flashpoints and heroics. Both give you superior gear and xp. I can essentially run the flashpoint over and over until I've got all the gear for my entire team. By the time I have all the gear, I've run the flashpoint enough that I can already move on to the next flashpoint since they are every 4 levels.

These are just my thoughts right now. I need to level more to see if I can keep this up as I get higher, but right now I'm skipping all side quests.

Thoughts?