Exactly. I combine that with /follow.

So if Xzin dies, I hit the Azin macro and then everybody /focus Azin and /follow Azin. The switch is nearly instant. Every spell requires a /assist focus string such that every spell can be changed on the fly to support a new "leader".

Of course I don't always do Azin but thats just an example.

I have one dedicated key for every character (all 10). The macros are all instantly viable again with new targets set. You can even go further and do more logic processing on the focus, such that it fails over if no focus is found or your main focus is dead (have it auto switch to a new focus target if main focus is dead, etc). You cannot auto switch follow though.