TRANOiD
I heard wymrest accord was good for rp. but this was like when wrath first came out so don't listen to me
Wyrmrest is still good. I hear Sentinels Horde has some pretty active groups.
I'm actually from Argent Dawn myself. There's some RP, but it's one of the oldest RP servers (dates from launch day) and actually is in a lackluster PvE focus. There are people trying to "revive" RP though here, but it's very small and clustered in a few zones.
Try to find yourself a dedicated RP guild, it's about where all the RP is anymore.