Kinda sucks they broke this...use focus macros for seconday holds and nukes on my setup and like the slaves to be 'target free' for the surprise factor. I have tried this out in the interim and it seems to do the job pretty well:

/assist main
/cast XYZ
/cleartarget

or

/assist main
/focus targettarget
/cleartarget

+

/cast [target=focus] XYZ

party1-5 would be fine except for battlegrounds - if you are set up like this and happen to not get leader or get an uncooperative player as leader, you're kinda boned.

-Xeva