Regarding wow warlocks, here's some of the things you can think about that are similar:
Sorceror:
permanent pets
escapes
aoe
lifetap (actually, stamina to mana)
roots and snares
disorient (like succubus charm)
Nightblade
drain health
aoe drains
DOTs
escapes
aoe fear
disorient
Dragonknight
fire aoe
aoe drain health
DOTs and more DOTs
roots and snares
knockbacks and stuns
Wings. Can leap like a metamorphed warlock. Oh yeah.
Templar
dunno... haven't really studied them much
Pet control is pretty limited, but if you're a fan of demonology, then go for Sorc. It's the only one with a pet. If you're a big fan of affliction, go for nightblade - they have a lot of drains and bleeds, but they have to be a lot closer to the action (just like how drain life used to be short range). Destruction is very much like the dragonknight who has tons of aoe fire abilities, but sorc has some decent aoe ability when combined with staff. As far as solo levelling, DK will own groups more than any other class. But a well-played sorc is incredibly hard to kill and almost as good at groups. Nightblades are not good at groups in general (ignoring weapon specific aoes) but are also tough to get your grubby mitts on because they're slippery.
The only think I know about templars it they have an entire healing line, and they have some powerful single target skills, but they are very much the opposite of the feel of warlocks.
Here's a DK firey build. I plan on making mine a little more warlocky with drains.
http://www.youtube.com/watch?v=zBzZYXqZCPA
Here's a NB drainer, but more of a test (not tuned with race) and not as effective, but I think it can be once you match it well to weapons and race. I think Force could've made this feel more like a warlock than it does, but again this was just a test he was doing.
http://www.youtube.com/watch?v=XFnKo1eMMHE
I don't find many high-level demonology sorc-style things. In fact, I almost never see pets out at high level, so I don't know if that means anything or not. But here's a kind of crazy farming video, and you can find many more.
http://www.youtube.com/watch?v=BYhx4TeIyEY