i just set this up for my 5 shamans ... i used a 3-step round-robin ...

1. /assist main
2. /interact with target (causes toons to run to target and auto-melee attack)
3. up-key (to stop the movement)

i hit they key 3 times quickly and it does the trick ... not sure if you can do them in less steps, but this works for me.

*edit* - click-to-move is a requirement ...