WW leeches life and mana just fine, but leeching enough to keep up with the mana drain on WW can be a little difficult. Keep in mind that with 5% leech, you'll only leech back 50 mana points on a 1000 damage WW hit. If you're in hell, that's only 17 points with the 2/3rds reduction on leeching (I'm not big on the stats scene, so everyone feel free to correct me here...). You also, I think, only get the leech on the damage applied to each monster, so if you hit something that is near death for 1000 damage points, but they only needed 100 before dying, then you only get 5% of that 100.
I had trouble with my WW Barb leeching enough in Nightmare and Normal difficulty, mainly because the damage on my weapon wasn't that great. In hell, I finally got ahold of a grandfather sword and haven't had any problems since. You mentioned that you've got a Manald's ring, which should help, so I'm guessing that you might not be hitting for enough damage. Or perhaps your AR is lower than it could be so you're not connecting too often. Finally, WW has two breakpoints on the weapon (-10 and -35, I think) that will allow you to hit much more per spin. Could you fill us in a bit more about your specific weapon, lvl, AR and damage figures? If you're high enough level, Tal's mask is easy to trade for with outstanding mods. I'm guessing that maybe your at a middling stage, so I can assure you that your mana steal will just get better and better as you level up and your damage increases. Good luck!
