Of all the classes in Diablo 3, the Witch Doctor was the one I was looking forward to the least, for the simple reason that while all other classes have skills that were either free to cast, or outright generated resource, the Witch Doctor doesn't. Every skill either costs mana, has a cooldown, or both. Furthermore, from level 6 on, mana regenerates slower than Arcane Power relative to the total amount you have (since your maximum mana increases by 50 every level), while the cost of your skills keeps climbing up and up and up. (For reference purposes, a level 60 Witch Doctor without any +mana or mana +regen gear would need 1 minute 44 seconds to fully replenish his mana from zero.) Fortunately, the Witch Doctor's niche is damage over time, whether through poison spells, pets or others. So if there's any class that can afford to stand there doing nothing for a few seconds, it's the Witch Doctor. (I guess you could also use a crossbow for those non-life-and-death situations, though I wonder how viable that option would be in Hell and Inferno.)
So what of the skills you'll be called to use in the early game? You start out with Poison Dart, a move that does your weapon damage from a range, but also adds in some DoT for two seconds after the hit. So it's not much better, if at all, than the other classes' level 1 skills, and it already costs something. Granted, it's not much, but in prolonged boss fights and other large mobs, your mana can run dry from your level 1 skill. Uh oh.
As with all classes, level 2 brings two new skills to the table. First is Plague of Toads, which not only seems functionally identical to the Wizard's Shock Pulse, but actually is, right down to the miserable range and accuracy. Of course, considering it costs mana (more than Poison Dart), it does a lot more damage than Shock Pulse, but it still blows. You can empty your mana bulb rather quick, and still not hitting a whole lot. The other skill is a lot more interesting, as Summon Zombie Dogs appears to be the Witch Doctor's bread and butter. Three tanks for a cheap mana cost, and they're so sturdy you're unlikely to have to recast them a lot, at least in the beta. In my run I've never ever had a zombie dog die, even against Leoric. I can't stress this enough: you NEED zombie dogs to stay alive and healthy, and they do an incredible job of it.
Level 3 brings about the skill that I arguably underestimated the most so far: Grasp of the Dead. I didn't expect it to be as useful as it was, perhaps because its range is a bit more generous than the graphics let it on, or maybe because while the damage numbers in the tooltips aren't THAT flashy, it can deal significant damage to large groups of enemies, to such an extent that main offensive skills like Poison Dart are much less needed, and mana is no longer an issue. Especially since Grasp of the Dead is so cheap, even at level 60 it costs less than 100 mana. Unfortunately, I was unable to use it much until level 6, where the third skill slot is unlocked, as I didn't want to let go of the zombie dogs, and Grasp of the Dead is very poor as your only offense. So I stuck with Poison Dart, added Grasp of the Dead as soon as I hit level 6, and will now probably be using this skill a lot when the game actually comes out.
Haunt is learned at level 4, and is a decent single-target DoT skill, but I didn't find it too compelling. The duration of the attack scales with levels, so it might actually be more interesting later on in the game, but so early it's just bleh. On to level 5 and Zombie Charger... another attack skill outclassed by Poison Dart. It moves so slowly, and has so little range... kind of like a less erratic Plague of Toads that shoots only once. It can hit mobs pretty hard, but you have to be up in their face for that. Even with zombie dogs it's not worth it. Then there's Hex at level 6, which summons a fetish shaman capable of transforming enemies into chickens, preventing them from attacking and making them take more damage from your attacks. Unfortunately, usually only one monster is transformed per use, and it's not always going to be the one you wanted. Especially against boss packs, though I guess I should be thankful that it can work on bosses at all. Sounds cool in theory, but in practice it's just not very good.
And the drought of good skills continue, as Corpse Spiders, learned at level 7, unleashes four spiders to attack for a few seconds... but the damage is laughable, and it drains mana quickly to boot. Then there's Horrify at level 8, which is meant to make monsters run in fear... but the problem is that it's a close range attack, and you need to be right in the thick of things to make the most of it, and it's something you want to avoid as a spellcaster. Heck, it didn't even seem to work all the time anyway, rarely did I ever get enemies to run away. Maybe it's because I wasn't close enough? Either way, it sucks, especially with the huge cooldown.
Things get much better at level 9, though, with Firebats entering the scene, finally allowing me to get rid of Poison Dart. About time! Remember Inferno from the first two games? Well, it's the same thing, except a lot better and cooler-looking. Without a Crimson rune the range seems a bit questionable, and while it's true that you need to be relatively close to your enemies, it's still a lot better than it looks, as damage is dealt even on enemies the bats don't quite reach. It's very effective against large packs of enemies, and at this point my strategy for every fight was, pop Grasp of the Dead, then while it's doing its job finish everything off with Firebats. Grasp of the Dead's presence turned out to be critical, as not only did it make battles shorter, but it also made it a lot harder for me to run out of mana. Speaking of which, Firebats didn't have the range and power of Disintegrate, but it was wider and drained mana far less quickly (I could keep casting it for 11 seconds at level 9).
Level 10, as with all classes, introduces passive skills, and the early choice this time was between a 20% damage cut to me and my zombie dogs, and a 20% damage boost to some skills, including Firebats. While more damage on Firebats is cool, taking 20% less damage from everything was way too appealing to pass up. It seemed to come in handy against Leoric too, as my zombie dogs were getting pounded on a lot, and only survived thanks to the health globes dropped by the skeletons he summons - and presumably that passive as well.
All in all, the Witch Doctor was honestly more enjoyable than I expected, though the huge mana concerns only start popping in later on in the game. The combination of Grasp of the Dead and Firebats really awakened me to the fact that spamming skills without end like in the first two games wouldn't work, and that you had to play more intelligently than ever. And since this is what Blizzard was aiming for... success!
Now, my brother raised a few characters all the way to level 13, the cap in the beta, so I tried the Witch Doctor and Monk to see what they learn after level 10. Starting with the Witch Doctor, it learns Firebomb at level 11, which is a very good AoE skill that can be thrown very far away, and very quickly as well. It decimated mobs with no problem whatsoever, but also caused me to run out of mana VERY quickly. I'd say that while Firebats doesn't do quite as much damage, it's a lot more efficient. It's really a matter of choice at this point. Spirit Walk is obtained at level 12, and there's not too much of a catch to it - you become intangible for a few seconds, which can allow you to escape tough spots. Not useful at all in a beta context, but in higher difficulties this might be interesting.
As for the Monk's last few skills, Inner Sanctuary, learned at level 11, creates an area monsters can't pass. Projectiles can still hit you though, and if you're close enough to melee monsters they can still swing and hit you. That means you'll have to stay idle for a while, which isn't too compelling. I think the only way this can work decently is with the rune that heals you while in the sanctuary, since you'd have a pretty good reason to stay back and do nothing then.
Exploding Palm, at level 12, was a huge fan favorite when it was first revealed, mostly with gory, messy graphics that were removed since then to make it easier to see what you're doing. And while the concept certainly sounds cool, the first two hits are worthless, since it's just relatively weak single-target damage, and the third hit's effect, where damage is dealt to nearby enemies if the target dies on said third hit or a few seconds afterwards, still doesn't match the devastating power of Crippling Wave. Once again, maybe in higher difficulties...?
As a closing note, remember what I said about using Shift to force your character to stop moving? Well, I decided to try out the button just to the left of 1 so that my hand wouldn't go all over the place trying to use multiple skills one after the other, and it works pretty well, though it'll surely take some time getting used to.
Well, that's three classes down, two more to go. Next up, the Demon Hunter... which is still allegedly underpowered compared to the other classes even after all the tweaks.