Loving my lock alt at the moment, heavy affliction spec so dot dot dot and the mob dies. Group of 3 mobs? Dot dot dot, change target, dot dot dot, change target, dot howl of terror dot dot and they usually all drop dead before they get back to me

Great mana conservation when I get it working well too, sometimes I run a bit low but generally I don't have to stop for a break unless I've had a tough fight with adds or on an elite or something.
Might be a bit similar to a shadowpriest; I respecced my undead priest to shadow the other day to have it a different spec to my draenei priest (I've always been disc or holy on priests before, never shadow) and found it a poor imitation of my warlock in playing style, in that I was just dotting and mindflaying (instead of drain life), but the priest has less options and kills slower - similar playstyles but warlock is way more fun in my opinion.