I'm still new to multiboxing, but at the moment, I'm running A prot pally, Frost mage, Ele Shaman and holy priest. They are all level 19 right now, but I'll be adding a balance druid to the mix at 31 (I have one waiting).

I use my Pally as my main character, with the others as slaves. I have frost bolt/lightning bolt/mind blast all on '2'. It's my main DPS button. I have instant casts like, Judgement/fire blast/earthshock all on '1'. I have a macro set up that will cast a heal on my pally. I'm not great with macros, so it's just something like, /tar pally, /cast heal.

So far things are pretty good. i've killed all the bosses in SFK with these four, except for arugal. I would highly reccomend using the tank as your main and the others as slaves.

The thing that I'm still trying to work out, is how to handle spot heals. I need to be able to write a macro that targets my pallys target and heals it. RIght now I just have my pally target whoever needs a spot heal, and then I usually have to wait 1-2 seconds (or it wont work), then hit my assist macro on my healer then cast the heal. I know there are macros that go something like /cast heal [target=pallys target]. But i'm hopeless with macros, so I'm going to need someone to write one for me :P

Anyway, I've started rambling. I suggest using the tank as the main. I can't imagine doing it the other way. =/