That clip is the cinematic teaser for a just-released 10-person raid dungeon, Zul'Aman. Like previous dungeons sporting the "Zul" prefix, it's home to trolls and their pseudo-Rastafarian, tribal society. You see, while they originally came off as pale imitations of pro-pot reggae aficionados, the trolls have developed into an amalgam of Haitian voodoo culture, shamanic animal worship, and of course, pale imitations of pro-pot reggae aficionados. You can consider that clip up their to be their own Braveheart -- well, you could if they weren't fictional, anyway.
The main reason I bring this whole thing up is that no matter where you place your unfounded hatreds regarding the MMO genre, and WoW in particular, you can't deny that Blizzard makes the finest cinematics in the industry. Even this clip which was entirely done in-game, is moving and engaging in ways that no Sarah Michelle Gellar television show could ever hope to equal. And once you've beaten Buffy, well you've conquered the world.
*cue moving orchestral arrangement, distant setting sun*