If I may suggest, and this is how I do most of mine anyways, even with ISboxer, Keyclone etc. I have this macro on my 1 key

/follow focus
/assist focus
/stop casting

Then I use the typical /castsequence [target=focustarget] on my spam macros.

Now for when I five box, on my left hand buttons, I have like

F1 /focus ToonA
f2 would be /focus ToonB

etc. etc.

This way, say ToonA dies, I hit the Appropriate function key, and keep plowing through.

Now granted, a lot of this is very redundant, given the built in functions of many of the programs, Isboxer specifically, But it's how I started doing things way back when with hotkey.net, and well, It's hard to teach an old dog new tricks. Not sure if something like this will help you or not, But If so great, If not, so be it, everyone has their own comfort zone, and that is cool also.

Stephen