It is very possible using LUA unlockers that bypass the limitations blizzard set on how scripts can affect the game. What its supposed to do, is vanish at the same time as a blind is directed at you, thus nullifying the effect of blind. this is pre cataclysm, although the script language is the same, but obviously, vanish doesn't work the same way as it used to, so its only beneficial before that time period, unless it keeps you in stealth even under the effect of blind in cataclysm/MOP.
Also, here is a clip I just uploaded of a vanish blind so you get a basic idea of what I'm talking about.
Vanish Blind example - YouTube Theres a little information in the video description as well