You may get rep from trash, but probably only up to Honored. I think I remember getting a little rep from the quest to go find them at the beginning of 5.2, the one you get from Jaina. Try the one where you collect stones to summon a the three types of bosses on IoT (Lighting, Spirit, and I can't remember the other one.)
Read the comments on the link you just linked. Its not for rep with them. The Only way to get rep is killing the bosses and a small amount from champions of the thunder king. You can only get rep from each boss once a week.
I think the only way to get rep besides killing ToT bosses is Shado-Pan Assault Insignia, which occasionally drops from the gold chests at the end of the Treasure Trove solo scenario, and from the chest you get after finishing Isle of Thunder dailies.