This is how I've set mine up. I have a Mage and 2 Elemental Shamen.

I have 3 different keybinds, one to set the focus on each DPS:

Tank targets the mob to be CC'd

Mage (ctrl+1):

/assist party1
/focus target

Shaman 1 (ctrl+2), Shaman 2 (ctrl+3) same macro as above.

Then I have ctrl+4 as the actual cast macro.

Mage:

/castsequence [target=focus] polymorph

Shaman 1:

/castsequence [target=focus] hex

Shaman 2:

/castsequence [target=focus] bind elemental

BAM!