It's been bothering me for a long while on what the art department was thinking on the Erinyes. as this link shows which is for the 5E, and has been the same since D&D has first introduced Erinyes, they have wings. And while yes they use a long sword, in combat Erinyes prefer using thier flaming composite long bow...
http://forgottenrealms.wikia.com/wiki/Erinyes
Comments
"After Asmodeus' ascension to godhood, the erinyes lost their wings, and received hooves and fangs in return, which made them look beastly."
Asmodeus ascends to godhood during the events of the Spellplague.
Featured Foundry Quest: Whispers of an Ancient Evil [v3] - NW-DQ4WKW6ZG
Foundry Quest: Harper Chronicles: Blacklake - NW-DCPA4W2Q5
*This note brought to you by someone who now counts eyestalks on every single Beholder she sees.
Basically all end game content is 5e. So theres no catching up its already there in 5e Most likely because Wizards made them do it. So yes it might have started out in 4e but quickly skips years and is 5e so gamewise it would be in 1491 or 1492 right now with the content of ravenloft being added in. Then soon after it will most likely be waterdeep.