The Hunter mana regeneration tool, Aspect of the Viper, has been revised again. Currently, in live, it provides passive mana regen. It was recently announced that it was going to be changed to provide 100% of your damage as mana regen, but cut your damage output by 50% (less with talents). This lets the hunter switch it on when they need mana, fill up their mana pool, and switch back to Hawk to DPS some more, as opposed to being in Viper all the time as many hunters do these days.
Apparently, though, it was just a bit too powerful, as many users have commented. Hunters with good gear were filling up their mana bar way too fast. So it's going to be changed again, this time to restore a percentage of your base mana each time you hit. While this does do away with some scaling issues, it seems to introduce others. For instance, this makes a fast weapon vastly more desirable for mana regen. But (say it with me) it's still beta, so I'm confident that they'll work out any game-breaking flaws there may be in this new incarnation.