In wow, make the macro

#showtooltip Heal
/cast [nomod, target=party1, help] [nomod] Heal
/cast [mod:shift, target=player, help] [mod:shift] Heal
/cast [mod:ctrl, target=focus, help] [mod:ctrl] Heal

With your G11, press the MR button, then the Gkey, press the key you want it to mimic then press MR again.

Viola.
Ingame if you hold ctrl and press the gkey it will heal your focus, or if there is no focus will cast heal on yourself (if you have auto self targeting).
If you hold shift it will heal yourself, if you just press the gkey it will heal the party leader (normally main)

/edit

Apparently shift doesnt work with numberpad keys, so make sure you macro your g11 key to something that you dont use which isn't on the numberpad!