Troll only:
- Shadow of the Empires (non-horde, all tribes): [Troll RP] Shadow of the Empires - 8 years of troll RP! - back in Zul'Gurub
- Zulian Legacy (horde), can’t find a topic but you can approach Tanshi!
- Gravesworn (horde, as linked above)
I would expect a lot more when Zandalari release, but Shadow of the Empires has been around for aaaages and so has Zulian Legacy and both are known for good quality, and Gravesworn is brand new but sounds promosing if you are a Bwonsamdi fan!
Mixed: (I cant post more links, but they’re around on the forums, anyways might not be what youre looking for since you mentioned troll only but these are heavy on trolls )
- Rastari Pact (Military, mostly troll)
- Hand of Zanchul (slavers, includes other races)