Why isn't scavenger Rey any good for sith raid?

I know all this. The only reason to run a potency set is if they just happen to be the best two mods (from a primary and secondary standpoint) that fit what he wants already, which is offense and speed. Specifically doing two potency mods for the occasional time where Finn goes first after a DN attack seems wasteful otherwise.

Not to mention confuse or mindtrick don't stack his tenacity since they do no damage.