I think you might be able to put a simple sequence in a GS macro.
PreMacro = [[
/targetenemy [noharm][dead]
/castsequence Deathgrip, Gorefiend's Grasp
]],
I’m not really sure if it would work, but I do know you can put sequence macros into GS macros. Most Frost Mage GS macros are like that.