I got things worked out last night, I was able to kill mobs basically non-stop finally. It does require more action then just mashing one button constantly, but I think for dual boxing that is expected. I have never tried boxing with more than two, but I think it might be simplier in a way because mobs die much faster. Dual boxing things are a lot more fluid since you can't simply one or two shot mobs when they are at your level. Both characters are mid-30's in level and lock is affliction and shaman is still resto.

Warlock has lead, sends in pet and waits about 2 seconds for it to establish aggro. Then warlock starts to fully DOT up mob, I start with immolate and run through all the DOTs then drain life. After first two DOTs, shaman starts spamming LB, this delay keeps aggro on pet/warlock. Mob dies, I life tap a few times while running to mob. If I need health shaman heals up while I loot and we are off again. If I am able to pull multiples, drop totems and follow same sequence except warlock fully DOTs first mob, then moves to next while shaman stays on first target until it dies then retargets.

I setup one DOT cast sequence for Warlock and bind it to two keys. The first key has no actions for Shaman, the second spams LB. I start with empty shaman key then move to key with LB after a couple of dots. This keeps warlock spells in the same sequence. This also gives me the flexibility to have shaman sit out a mob and regen mana if he needs to so that he doesn't need to drink.

For drain life, I have one key bound with no shaman action, the other casts a long heal when I need health. I also have a key bound to heal warlock, shaman or pet in combat.

This may not be the most efficient setup, but I was looking for something that I could quest with non-stop and keep things relatively simple. Shaman might be more effective as elem and I may test that out one night soon.