As far as I can tell by logging in and out in different areas and with robes / cloaks on, this problem is fixed by the newest NVIDIA update. That's GeForce Game Ready Driver version 390.77, which was released today. Hope it works out for everyone.
All the weird graphical glitches involving robes and cloaks disappeared for me.
Thanks for bringing this up. I've installed these drivers and logged in. So far so good. I'll re-post if the issue persists.
