If you use "focus" as your primary means of assisting/targetting you could set up a couple hotkey macro's for changing your focus. Such as using F9 to make your hunter the focus and F10 to make your Priest the focus. Then all of your macro's could be built upon 'assist focus."

For fighting here an example of some macros if it helps. I would have the following macro's bound to my "F" key.

Priest:
/assist focus
/castsequence reset=target/combat Smite, Mindflay

Hunter
/assist focus
/petattack
/castsequence reset=target/combat Serpent Sting, Arcane Shot

I use my number keypad for my main character, use the regular number keys for my clones, then create a couple battle macro's that auto assist and cast spells.

As far as buffs, I use SmartBuff add-on which casts buffs with a scroll of a mouse wheel based on my settings so I don't have it taking up slots. Auto-bar is another good add-on which you can bind keys to without taking up action bar slots for using items/food/drink/scrolls/etc.

Just suggestions, hope this helps.