I don't believe you need the "[pet:Felhunter]" in there.

SPriest:
/castsequence reset=24 Silence,,,,

Warlock1
/castsequence reset=24 , Spell Lock, , Death Coil, ; ,Death Coil

Warlock2
/castsequence reset=24 , , Spell Lock, , Death Coil ; , ,Death Coil

Remove the Felhunter part and it should cast deathcoil in sequence. The problem is it's trying to cast deathcoil from your felhunter. This is my best guess, as I'm not a macro pro. I'm kind of wondering why you have multiple deathcoils in your sequences, since deathcoil has a semi-long cooldown.