3. Macros - What can they not do?
Macros cannot make smart decisions for you. They can’t cast spells based on cooldown, or check if a buff is active, or magically fit all your abilities onto one button.
Macros cannot be any longer than 255 characters, unless you use an addon to circumvent this limit.
Macros cannot circumvent the global cooldown to use more than one item or ability at a time. There are some exceptions, but this is the general rule.
Macros cannot simulate additional keypresses. One keypress = one action.
Macros cannot include a delay for most commands. Certain commands (e.g. chat) can be delayed with an addon.
Best that you can do is a help/harm macro.
#showtooltip
/cast [mod:alt,@player] [@mouseover,help,nodead] HELP_SPELL; [@mouseover,harm,nodead] [harm] HARM_SPELL; HELP_SPELL
or variant
#showtooltip
/cast [mod:alt,@player] HELP_SPELL; [@mouseover,harm,nodead] HARM_SPELL;[@mouseover,help,nodead] [help] HELP_SPELL; HARM_SPELL