I dual boxed warlocks and this is the main cast sequence macro that I use on them.

(I'm not sure at what level exactly you get most of these spells, but you can use what you have now and add as you go.)

Warlock 1 - /castsequence Unstable Affliction, Curse of elements, Life Tap, Drain Life, Drain Life, Drain Life

Warlock 2 /castsequence Corruption, Curse of Agony, Life Tap, Drain Life, Drain Life, Drain Life

(This is a rough guess, as I am currently at work, but I'll take a look tonight and see exactly what I am using)