Bloodlust is perhaps the most valuable skill you can have in WoW The War Within, but it's limited to a few classes.
The War Within Class Selection Guide (Spec & Hero Talent Preview for ALL CLASSES)
A Bloodlust effect or ability increases Haste by 30 percent for all party and raid members for a whopping 40 seconds. It’s the most broken ability you can use in PvE content, and it’s especially important for raids and Mythic+ dungeons in The War Within.
Here's our full guide to all the classes with a Bloodlust effect and other versions of Bloodlust in The War Within.
As the most powerful ability in The War Within, only four classes have this effect built into their kit: Evoker, Hunter, Mage, and Shaman. The Bloodlust abilities of those classes are all identical, save for their names. So, having at least one of those classes in your party is essential when doing Mythic+ dungeons and Nerub-ar Palace Raid.