the Crouch family is highly respected and pure-blood and related to the House of Black, but the HP Wikia doesn't list them as nobles), is old, and canon seems to imply he was powerful & competent in Dark-hunting

Not just imply, I'm pretty sure that in the fourth book Dumbledore explicitly calls Bartemius Crouch "powerfully magical."

The relevance of that may be limited if Eliezer hasn't read the book itself though.