My toons are: V, T, A, E, and R.
My spells are cast by assisting Party1, which leaves focus free for other functions.

Create one macro per toon, each on a different keybind, so pressing the keybind sets focus for that one toon only and does nothing for the other 4 toons.
I'm thinking:

/Assist [target=Party1]
/Focus
/Cleartarget

Then create five focus fire macro's (on my Shaman's).
#showtooltip
/Castsequence [Target=VyshaFocus] Spell 1, Spell 2, Spell 3
My question for the focus fire macro's is the syntax.
Can A, T, E and R use [Target=VyshaFocus] ?