I get my rep from doing invasions when possible as well as doing the dungeon grind. Valajar Rep and High mountain rep is given through one of the bosses in each of those area's dungeons. Its about 250 rep per run. Killing Odyn in HoV gives you 250 rep with the Valajar and killing the worm boss in NL gives you 250 rep with Highmountain. I have never seen REP gains from EoA or DHT, but I could be wrong about it. Its a grind bro.