I'm Melee\Close combat specd for my Sunsinger. The Flame shield and high armor is great. Though had a period where i had high discipline and used nade spammed everything as a sunsinger. Try to have more range with my Voidwalker though as its not as melee friendly as Sunsinger to me. The Melee drain is nice and all but you can also apply that to grenades if you want though. I got for more AoE with voidwalker and more single target with my Sunsinger.

It depends on whether you need this for pvp or pve. But you can use what you find most versatile. What can be applied to most situations. Let's say you're a Hunter and you start blade dancing. Well that's fine in Crucible, but would that work against Atheon? Hell no lol! Now, speaking of Warlocks and fpshooters in general, grenades are extremely versatile in a variety of situations both in pvp and pve. Your Super and Melee Special compliment you, but are a bit more situational. Melee requires close quarters and Super depends on what the current goal is. But nade's can be chucked into just about any situation. Go Discipline, then decide what you want more of between Intellect and Strength. Pay attention to what you find yourself consistantly using more as well as personal preference.