/focus [target=suicidalheal,nodead,exists][target=deathbytotem,nodead,exists][target=player]
/assist [Target=focus,nodead,exists]

I think but i'm not sure, this is something along the lines more of what you need. it will set focus on on ether suicidalheal or deathbytotem, but it will only do so if they are not dead and if they even exist. Then it will assist them, but only if they are alive/exists. Im assuming if your main does not exist you will be just switching over to the new main toon. whome ever that may be.

Home this helps, if it does sry =P