Yeah, somehow I can see us trying to stack SPD/DET. With so many low damage attacks we are more negatively effected by rounding on Crits than other high damage classes (cough, BLM cough). If SE changes it so everyone has a static Crit Chance (with Crit only effecting the damage of a crit) - Then with our pets we will already have the highest chance of Enhanced Pet Procs for higher Spell Speed. So there shouldn't be any reason to stack Crit over SPD/DET.
But yeah, Spell Speed for sure. Gotta get all those Ruin III's off during Dreadwyrm Stance.