The Warlock melee is absurdly long distance (I play as a Warlock 90% of the time), I will admit that. However, the long melee (especially with the Stormcaller subclass) is useful in certain circumstances. The Voidwalker could easily be used in a grouping of Thralls or Dregs to cause them to explode with the perk (forget the name, but the same perk applies to Sunsinger). Stormcaller, basically you can chain your melee if the perk is selected obviously. However, the chaining deals less damage the farther from the source (based on what I've seen, especially on Plaguelands and Dreadnaught patrol). Also, how could a Warlock, on PvE, be killing you..? Unless they're getting in your way and causing enemies to damage you heavily, there's no other way for them to "kill" you.