I use focus on my main. I use /cast [target=focus-target] DPSSpell for damage and /cast [target=focus-target-target] HealSpell for heals. That heals whoever has aggro from the mob your main is targetting. You can add in an extra command to heal anyone you want. It becomes:
#showtooltip
/cast [target=focus-target, help] HealSpell
/cast [target=focus-target-target] HealSpell
/cast [target=player] HealSpell

You can still target a mob to kill or person to heal even if you are dead, but incase the alts don't have a focus, the last one heals themselves (just in case).