I'm at work so I can't test this but try:
Code:
/cast [nopet,combat]Fel Domination
/cast [nopet]Summon Imp
Or if you're feeling flash:
Code:
/cast [nopet,combat]Fel Domination
/cast [nomod,nopet]Summon Imp
/cast [mod:shift,nopet]Summon Voidwalker
/cast [mod:alt,nopet]Summon Succubus
/cast [mod:ctrl,nopet]Summon Felhunter