Surv hunters in the opening tier (maybe 2) of wrath are one of the better replen sources which is a major source of mana for all your healers and even useful for many casters. Other specs that bring it are frost mage, destro, shadow, and ret. To my understanding ret isn't great in early wrath but is quite strong later so if you are meta comping you want a surv hunter early who can go marks when they have the arp for it in uld/togc and you get a ret pally for replen to replace them or a spriest. This is just from what I've been told by some one who pretty much lives in the hunter discord.