Mana is the Witch Doctor's resource. Mana functions similarly to the way Mana acted in Diablo II. It is a large pool that will increase as your character's level increases. Higher level skills and more powerful skills will cost more Mana than lower damaging spells. After exhausting your Mana, the globe will slowly refill back to full; different from arcane which fills much quicker. The Witch Doctor also has many skill and passive options that will help him keep his Mana replenished and not have to wait for it to slowly refill itself. From my play through with the Witch Doctor, all but one skill had cost so little Mana that I was actually able to spam any skill indefinitely. I am sure at higher levels this will not be true but for the beginning, it is practically unlimited. However, once the resource was emptied, it was very damaging to wait for the globe to refill itself, especially when fighting the Skeleton King. Managing this resource and finding ways to rebuild it quicker will definitely be a key strategy to playing this class.
Zombie Charger is the next skill you get which is a short range zombie that rushes in front of you for a short distance attacking anything in its path. However, given is very short range and myself staying away, I rarely used the skill. Hex followed which summoned a Fetish Shaman that would run around turning monsters into chickens. As far as using it for CC, it was pretty ineffective because it was only one monster at a time when there was usually five to ten. However, the nice part about the skill is that the chicken'd monster does not break out when damaged and actually takes more damage when changed. When used on champion and harder monsters, it helped to drop them quickly while they were unable to do anything. Corpse Spider is a temporary summon that released multiple spiders that attacked nearby monsters. Although I wanted to focus on any summoning, their temporary state made it insignificant for the few skill slots I had available. Horrify became your "Oh Shit" button when surrounded by large groups. A quick way of avoiding a quick death. Once more skill slots are available, I could imagine it being very useful. However, the beta has only three to four slots making skill choice very important and I didn't end up using it that much. The last skill I got was Firebats, a short ranged AoE that attacked anything in front of the Witch Doctor. The range was actually surprising large and the damage by level was impressive and became my main attack. It mowed down most monsters within seconds. However, because it is a channeling spell, it was the first time I actually saw my Mana drain. There are a few more skills that are available for the beta but I did not get to a higher level... yet.
The look and feel of the Witch Doctor was amazing in my opinion. Starting off, I really enjoyed the voice acting for the male Witch Doctor. Not too overdone, it definitely gives you the feel of this tribalisitic character. His gear equally matches this feel. With the same gear looking different on each class, the Witch Doctor's gear was great at looking strong while keeping the minimalistic look of the Witch Doctor. I also enjoyed at one point where the character falls down when entering Tristram Catherdral. While most classes do so with agile or strength, the older Witch Doctor actually looks like he is falling giving him this cohesive feeling.
Overall, I loved playing as the Witch Doctor. I planned on playing this class first and he was the character I selected when I first logged in. Starting off with my Zombie Dogs, I enjoyed the summoning aspect of the class, saving me from having to click on every single monster to kill it. I was also able to find a good mixture of skills that allowed me to keep my distance. The odd part about the class is that you can choose to stay away with many skill choices or getting into the fray with the multiple close-ranged skills. The Witch Doctor really allows you to have a wide range of viable builds to match your play style. I found myself able to stay away while still being in the action while my zombie dogs chowed their way through the mobs. As mentioned earlier, once I had Firebats and my Mana actually drained, I found running out very debilitating. King Leoric was especially tough when he took out my minions and I found myself without Mana and just having to stay away until it refilled. I planned on this class being my favorite and so far it has not disappointed.
You can watch Force play through as a Witch Doctor as well.