Originally Posted by
Sci Fi Samurai
Warlocks are intrepid scientists, studying forbidden magic and pursuing dangerous knowledge, often for the power, but other times for the scholarly pursuit of it. You'll find a mix of imbalanced brilliant meth heads among them as well as genius social outcasts. Anything less tends not to stick around very long; it is not a path for the weak, timid, or reckless (well sometimes reckless).
Their use of fel energy has traditionally been very broad while demon hunters are much more focused. Warlocks study and experiment with a subject, discovering a variety of avenues in which it can be used, DH's absorb the fel power into themselves for the singular purpose of gaining power. There's overlap, except that, for DH's, power serves the purpose of destroying demons and is combined with more overt martial prowess. Think of DH's as just taking a piece of what a warlock does and then combines it with some rogue skills.