Sentence:  A big mistake I see a lot of warlocks do is <WSD>overpulling</WSD> with whatever demon they're using. VW's good for two (maybe three), but the succubus is only good for one at a time. But young warlocks don't know this, so they send their demon into a pack of mobs, start up with their DOT's and suddenly find themselves in the middle of melee because the demon can't hold aggro. 
Meaning of the word marked with <WSD> tags:  To lure away more monsters than one can handle in combat.