Vyndree your video is fantastic, it helped me months ago get started. It doesn't quite help him for his multiclass multiboxing.

Basically, you'll bind a DPS rotation macro (or specific spells/abilities, your choice) to your rogue (rouge for some of you) and leave those blank on your mage. For your mage, do the opposite.

For instance, On my warlocks, I have keys 1-5 as various macros and abilities that only the warlocks can use. I have keys 6-10 for my paladin (on the paladin, he doesn't have anything bound to 1-5) and then a couple things on - and = that they both can use at the same time. = is summon charger/felsteed, and - is demon armor on my locks and righetous fury, or whatever my threat increase from holy damage buff is, because they both have 30 min intervals.

If you have a macro that does a DPS rotation (ss, ss, ss, evicerate or whatever, more, more, more) on your rogue and one on your mage (frostbolt, fireball, fb, fireball, etc, etc) then you can put them both on the same button number (say number 2) and just continue to spam press that button until things are dead.