I drive from the healer.

I use naga buttons 7-12 for healing.

7 - party
8 - mouseover
9 - party
10 - party
11 - healer
12 - party

Tank is standard IWT setup for melee. For a while I used 3x hunters for the misdirect simplicity to hold aggro. It works really well.

For any other DPS team I would just setup a key modifier to send the tank in first and then release the key to have the dps do their thing.

The naga allows me to focus heal when needed and the buttons are coordinated to the grid config on my screen. So I know who gets healed on button 7, 8, 10 and 12. I have tried many different heal setups but I think this one is tops.