I am afraid I don't have any of these discs but I've read up on them at some usually reliable sites and they all say that the 3 Eastern movies actually have the English dubs. You may want to check out these reviews (including screenshots at the bottom; click "Weitere Bilder" to see some more):
CHEN SING also includes a slightly longer version of lesser quality as an extra that apparently doesn't have English audio.
WU KUNG also includes a slightly longer cut of lesser quality as an extra but, alas, without English audio.
DAS TÖDLICHE DUELL DER SHAOLIN includes a slightly longer version of comparable quality as an extra that also has an English track.
BARBAREN/IRONMASTER has been put out before by MIG Films in a movie collection that promised English audio on the back cover for all 4 included films, but didn't actually provide it on the discs. What a blunder! Unfortunately, the Voulez Vous single release doesn't offer English options, either. I suspect it's just a repacked MIG DVD, which would explain why the wrong information on audio options can still be found in most product descriptions online.