I thought I would add my macro for critique:

Step 1:
/stopmacro [channeling] #avoid interupting a manual hymn (typically)
/stopmacro [@mouseover, exists,help] #stops the macro if I am manually targeting
/cast [@tank,exists,nodead] Power Word: Shield

Step 2:
/stopmacro [channeling]
/stopmacro [@mouseover, exists,help]
/cast [@tank,exists,nodead] Prayer Of Mending

Step 3:
/stopmacro [channeling]
/stopmacro [@mouseover, exists,help]
/cast [harm] Holy Fire (4.1 will greatly improve HF so I have it in now)

Step 4:
/stopmacro [channeling]
/stopmacro [@mouseover, exists,help]
/cast [harm] Smite
/cast Archangel
/cast Power Infustion
/use 13
/use 14

This essentially keeps Power Word Shield, Prayer of Mending on the Tank when the cooldown / debuff is ready. This also keeps Holy Fire on the target on cooldown and simply smites any other time

I then use ISBoxer regions when I mouse over a target to issue a command of /stopcasting and since each macro has a condition to check if a mouseover exists I enter full manual healing mode.