Escher males may be useless, but if everything is working properly, 80% of them should be females. And the Goliaths, despite being made up entirely of Fist of the North Star villains, can actually make decent use of their females since they're only bad at combat. I'm actually not sure if the Delaques are any good at anything - it would be a lot easier to give them a niche if you could put stealth to any sort of use in Fortress Mode beyond hunting, but at the moment they're only really there for flavour. One of the things I've been considering is to make it so that in Fortress Mode, every Hiver civ will exist and have the ability to steal, siege and ambush, so that as Orlocks, you could have year-round attacks by Cawdors, Goliaths, Eschers and Van Saars in addition to Delaques and all the regular baddies, but I'm not sure if that would be a pain and I haven't had a lot of time to sit down and test fortresses.
As a side note, I've put the Enforcers back in too. At the moment they don't do much of anything, since they neither siege nor trade by default, but I've been considering certain circumstances where you might get a siege from them via DFHack.
EDIT: Aaaandddd it looks like despite the fact that IMMOBILE creatures can now attack and use interactions, they do this very, very slowly, as they spend most of their time between shots wondering why they can't move around.