Help with a DK opener

im completely new to this and am wanting a 1 button spam for an opener as I have a hand issue.

/castsequence reset=60 Outbreak, Festering Strike, Summon Gargoyle, Dark Transformation, Death Coil, Death Coil, Death Coil, Unholy Assault, Empower Rune Weapon, Apocalypse()

is what I have, however things like DT and ERW arent on GCD so this essentially wastes 2 GCDs. How do I optimize this.
The reset is only because as an opener button i just want it to stop after its complete as i wont use it again afterwards.

Thanks for any help!