Use Your Gamer Launch Account
Your account from any Gamer Launch site is valid here.
If you already have a Gamer Launch account connect your Facebook account on your user profile first before using Facebook connect to login. Otherwise you may end up with a new account.
If you are in an instance and notice something strange, go ahead and test it out. For example, in the Battle of Lorien, we noticed that sometimes a Pulpum Berzerker will add to a pass being defended. After testing it out, we found that they add if the pass is not defended quickly enough. This adds to the importance of high DPS on the defending team. So form a theory and test for that theory. It may make all the difference in a raid or instance.