It's not like we've had a metric shitton of troll raids... There were three troll bosses in ToT, and the rest of the raid was Lei Shen's flunkies or the creepy beasties that lived under the palace... before that, the last troll raid was literally when ZA was a new raid in BC. That being said, I don't see there being a troll raid in WoD, simply because there are no trolls on Draenor except for the ones going there thru the portal.
http://www.wowwiki.com/Dentarg
He should be a raid boss
Ner'Zhul won't have any Ogre Magi servants in this timeline though