Currently on act 3 inferno, play solo and with some friends (DH, Wizard until our monk gets geared).
Right now, it seems you either go with a VQ build with Zombie Bears/Direbats (they seem to die out after act I), or with a splinter-dart build. There seems to be no other viable choices, and I think that has to do with the fact that pets are utterly useless, and that we don't have any other spell that compares to splinter-darts in term of single target damage (which in my opinion seems significantly weaker compared to other classes skills).
Currently I use fetish army runed with legion of daggers to recreate what a pet is supposed to do: be able to tank an elite for a few seconds at least, instead of getting one shot (of course the little guys get destroyed too, but usually it takes the mob more than a single swing to kill them all, which gives me some time to squeeze in some dps). I'm not sure if they were meant to be minitanks, but with the absence of pets, they're the closest thing to a proper pet that we currently have.
I was in fact getting sick of playing my WD because they seem very underpowered, and then I started playing with a couple of friends of mines, and it's been a blast. We kite everything, and I finally feel like my wall of zombie, my snares and whatnot actually feel powerful, and then it finally hit me: even with the Pierce the Veil (20% damage passive) i'm not gonna be able to outdps a similarly geared DH, but I will be a useful support class.
Now, having played a warlock in arenas to 2.2k+ rating, I understand what it's like to be mostly a support class, or a third wheel so to speak, but i'm not sure if that's what I want to do. And I also realize that a damage buff (like for example making spirit bomb a very powerful spell) AND a pet buff on top of all my other tools would make the WD a very overpowered class.
So, what can be done? i'd actually look at the mana cost of some of our damaging spell and the damage they do. You can't use direbats without vision quest, using darts is dumb without pierce the veil (which increases mana cost too, but darts are very cheap), and spirit bomb/haunt don't do enough damage for their cost. It seems fixing the mana cost and the damage of some of the other spells would bring diversity back into builds, and if done correctly, would not make us OP. A pet buff seems necessary too, I honestly feel sad for the devs that put so much into making these cool pets that we can't use on inferno, and i'm not asking for a perma gargantuan that will tank better than a 900resist Barb, but rather something that is able to tank an elite/champion pack for 5-7 seconds, similar to our fetishes.
If we're going to be a support class, then make us feel useful, and if it's not your intention to make us a third wheel, then please revisit some of our less used spells and make them compete with some of the stuff DH/wiz have. I'll continue to play this amazing game, but I'd really hate getting to diablo on inferno and realize I should've rolled a DH or a Wiz.
Also, kind of unrelated, Spirit Vessel doesn't seem to proc at times, and when it does the spirit walk that activates is unable to go through mobs, like our normal spirit walk does (not sure if intended). Also let our Spirit Walk be able to go through the mob's walls :P!