Not much to add - Try Input Director (link at the top of the software forum) instead of synergy if you're only using synergy for mouse-sharing.

Other than that, it's pretty much just a process of figuring out what works best to switch on the fly for you. I personally use a /assist and /follow macro(s) that are setup to follow/assist my toons in a specific order, so if my main dies, I swap to toon#2 in the list and keep on fighting. Most of the kinks I ran into had to do with my slaves still trying to use my mains target, or to follow the dead toon etc. Once I had those macro issues sorted out things fell into place pretty nicely.