Basically needed to change to:

/tar [target=focus, nodead] focus
/stopmacro [target=focus, exists, nodead]
/assist MasterToon
/focus

Will place that macro, on each of the slaves.
Each will have a slightly different keybind, so each slave can have its own focus.
Pressing the button again will have the slave re-target their focus.

So can set A to focus healer 1, E to focus healer 2.
Then mid fight, have A/E Hex their healers, and have V/R each assist to re-Hex with a castsequence.
At least if it works how I'm hoping.

Worst case scenario, I'll be able to focus fire on my current target, or either of the four focus targets.