If you want to make your focus targeting a little more flexible use this as your FocusAssist macro
Code:
/target [@focus, exists, harm]
/assist [@focus, exists, help]
/stopmacro [harm,nodead, exists]
/click FTLAssist
This way if you set your focus to a friendly your chars will assist off them, and if you set the focus to an enemy your characters will nuke it.