I've just found them super useful. Their damage isn't incredible, but ignoring Incorporeal, Hard to Wound, Terrifying, Manipulative and Friendly Fire makes them really consistent. They often get some early shots in, then one of the J's rushes in to engage and they either get to finish it off to free a beat up to keep going or put in damage on whatever tried to take down my beater.
That said, they definitely get a lot better against undead. Luckily, False Accusation is actually quite powerful as a free action in the crew in general. Mental Trauma is nice, but just opening up something to Into Dust can burn the opponent's hand and stones a lot quicker than they'd like. This is particularly true with 2 of them, as up to 4 of those shots gets people cheating some high cards against an ability that "only" makes them count as undead.
Don't discount Final Rest either. It's a good size pulse that can really mess up certain crews and even when it doesn't the heal having essentially unlimited range can bring one of the J's back to a point where the opponent is just out of options to finish them off.
I generally run the pair along with a recruiter as a little module of its own. Getting a couple DMs out of them almost makes the recruiter worth it.